Can anyone recommend a place I could buy one? How do you bend them to form to the stick properly

Not sure where to find them, but you'll just have to do some searching. Maybe someone that has purchased one someplace can make a recommendation.

As far as fitting onto your hiking stick, just bend it and nail it on. Maybe bend it to a slightly smaller diameter stick first so when you put it on your hiking stick, it will lay snug. Use a small dab of glue on the back and nail it on.

I found a couple places online to buy a medallion:

https://hikeamerica.com/product/boundary-waters-state-park/

This is from the Boy Scout base in the BW

And here's a thread from 2014 about attaching them to a stick:
old medallion thread

I've seen people with different medallions all over their sticks liked the idea of carrying all the memories with you on a hike. Guess you could even put them on your paddle and have a record of all the different places you've been canoeing!

I have made multiple purchases from Hike America with no problem. This thread reminds me that I need to order a couple of Devils Lake State Park medallions.