Depend on where you start but you will find that the shell can be bought almost every where on the route.
They are pretty easy find at just about any town with more than 100 people. If you want to get one there, you'll have no trouble.
I don't know if there is a Confraternity of St James in the USA but when I joined the one in South Africa, I was able to bought my Pilgrims Passport (for the stamps "sello's') and also a badge for my back pack in advance. I see there is a forum "American Pilgrims on the Camino" on the internet - surely they can help you.
Yes, here we have a chapter of the Confraternity of St. James-American Pilgrims on the Camino is it!
http://www.americanpilgrims.org
Great place to get a (free) pilgrim's passport. It is, however, small. If you start from SJPdP you'll likely need a second. They also have local groups that can be very valuable. In fact our local group is having a get together this weekend.
Some (or all?) chapters of the American Pilgrims on the Camino association hold "
Camino de Santiago Shell Ceremonies" for departing pilgrims. I think this tradition hasn't reached us yet but I am sure it is just a matter of time
.
Some churches here in the states do them. It's not a regular thing but they do happen. APOC is handy for finding out about the where & when as well.
I like the notion that my shell, which is sitting with my compostelas and credentials in a display case, has travelled every step of two Caminos with me. It fits in the case a lot easier than the other things that accompanied me each time, ie., my backpack and my wife.
I like this notion as well. I left my house with a shell that my oldest daughter found for me on a beach in Charleston, SC. Oddly enough, by the time I reached SdC I had three. The one my daughter gave me, one that I bought in SJPdP as I was leaving town (why, I don't know, it just felt right), and finally one that was given to me by a Spanish family member. That is story in and of its self, and a bit off topic. All three are special to me for different reasons.