Peaceable Projects Inc. is a U.S.-based non-profit group that brings the vast resources of the wide world together with the ongoing needs of the people who live, work, and travel on the Camino de Santiago pilgrim trail network in Spain.
I'm not sure where you live, but you might take a look online at L L Bean. I have never purchased anything from them, but I know they carry plus sizes. It's hard to shop at sporting good stores because, of course, athletic people are not heavy! Yeah, right! Even if you find something in an XL it's not always large enough. I did purchase my hiking shorts and a wind jacket from REI. I have purchased work out tops at JC Penney and Macy's. Sorry I can't be of more help, but good luck with your hunt.
Columbia carries hiking pants up to size 24, and tops/jackets up to 3X. Actually, some of their men's clothes go even bigger (my first rain jacket was a men's size 4X - but I was lucky enough to have no rain on the 10 day hike and never actually wore it!). I've also gotten lightweight workout / hiking clothes up to 3X at Nordstrom, Target, Old Navy, and JC Penney.
As far as what might be a good fit, you'll really have to try things on. The hiking pants I had from Columbia were actually a terrible fit, and I ended up just wearing workout leggings every day!
A couple of days ago, I bought a men's merino wool lightweight t shirt in a size small, since the women's merino shirts were both more expensive and more fragile. I usually wear a women's medium or large. At the same time, I bought a pair of men's lightweight hiking boots. I have never worn women's boots, because they do not fit me. You will probably need to get women's hiking pants for fit, but for thirty years I wore the same jacket, which I bought for very little at a Western wear store in western Canada. I don't think it had a gender, but if it did it would have been menswear. It finally wore out on me. Consider that some loose fitting garments - t shirts, a fleece, may fit you just as well if purchased in the men's wear section. That will give you more options in the larger sizes. For years, I wore a fairly large fleece which I picked up in a second-hand store for a couple of dollars. I never inquired about its gender. Good luck in finding what you need. I have just spent a small fortune re-supplying my gear and clothing for my September camino. Lightweight and good fit are great, but cheap would be nice too. Good luck.
Camino de madrid, camino francis, camino inverino (2012, 2013,2014)
CdM, Francis, San salvador, primativo june 2015 CDM , francis, inverino 2016
Camino madrid, via de Plata. Santiago.
Coast of the dead malpica to muxia
One of the items I wore last year was a mens long sleeve Helly Hansen tshirt. It was really too big for me but covered my arms and was nice and loose so didn't trap the heat so much as the fitted ones. I picked it up at Sport Check. It wasn't pretty but it served the purpose, washed and dried well and was great sun cover. I trashed it when I got to Santiago though.
Not knowing where you are and what you consider plus size I can only tell you my picks. I wear North American size 14. I wore Eddie Bauer Travex pants and capris (size 16 - a bit loose but comfortable) Eddie Bauer lightweight micro fleece, Underarmour t-shirts and Costco long sleeved Merino wool top. All tops in women's XL.
If you are not in North America, I think most can be purchased online.
Enjoy your planning and Buen Camino.
I'm also plus size and had a Macabi skirt which worked well for the camino. They have up to size XXL, check their website. I really like the Columbia Tamiami II shirts in either short or long sleeve and they have sizes up to 3X. Pants are always difficult. I've been purchasing men's but I'd rather wear the Macabi skirt.
Make sure you purchase clothing before you go to Spain as you won't find many or any plus size clothing when you get there. If you are in the US check Sierra Trading Post. I have purchased the plus size Tamiami II shirts there as well as a plus size fleece from the website at very good prices. Be sure to sign up at their website, then they will send you emails for even better prices, like free shipping and an additional 20% off. Also check ebay for plus size or Amazon.
I love my Altus poncho - I bought it online from Spain. I have a size S/M and it measures 72" (= 180cm) in width. It is designed to go over a rucksack when the vents at the back are unsnapped. (they give extra length rather than width). I'm 5ft 4" (1.63m) and it reaches to about half way down my calves.
When I am not at my fighting weight (meaning off diet and exercise...) I wear a medium or large in my Macabi skirts. The place I have terrible problems fitting is my lumpy dumpy A-cup upper body. Because I hate the feel of synthetic fabrics (except polar fleece - my hands tingle just touching it and it gives me the heeby jeebies having it on me) I try to purchase tech clothing way large than I need. Fine and dandy except even on a good day XL's are way too small and men's cut fit strangely!! Can anyone suggest tech clothing lines that run large? (USA) That info might be helpful for a bunch of us too!!
I have tried UA also but the loose fitting aren't loose enough and the fabric still drives me batty!!! I have 3 short sleeve and 1 long sleeved Exoffcio JavaTech shirts that I only use on my camino trips. Love them but would love other options too!