The rule of thumb I learned over some 10 years of Camino related activity, is to keep with you anything that, the loss of theft of, would effectively end your Camino or make proceeding a real hassle. I include optional items like cameras, etc. for those who have expensive gear in this category.
Also, keep with you ALL identity documents, credit cards and money, small electronics, prescription medications (don't worry about nutritional supplements - you will survive until these can be replaced). Bottom line - if replacing an item would be impossible, very difficult, expensive, or time consuming, carry it with you at all times.
Everything else can be replaced in or near any large town or city. There are Decathlon sports super-stores, and many, many smaller local businesses, catering to the pilgrim's needs. Just ask around if you lose something along the way. You can also Google search for "sports supply store near me."
In a city, I usually Google "Decathlon near me." Most are just outside the city center in a light industrial or "big box store" area. You might have to take a bus or taxi. But, needs must. if this becomes the need, ask around for others to go with you and share the taxi costs.
Also, I leave my phone charger and cord in my backpack, but I keep a battery pack with me. In town, I use a small Sea-to-Summit sil-nylon, 16 liter, zip top shoulder bag worn crossbody, or a fanny pack worn the same way.
This is definitely a case where an ounce of prevention is worth several pounds of cure.
Hope this helps.
Tom