Hey there, nonny, thanks so much! I actually know very little about spirit keeping- I’ve only just begun myself, and that was half an accident because I traded for a pelt that happened to have something still attached. You don’t have to buy a spirit, though what I hear is that spirit binding is difficult, so I would leave it to people who’ve been doing it for a while rather than jump in headfirst as a beginner.
I looked through my archives and don’t seem to have any resources on hand; but I know of a few people who do keep spirits. Try looking on serapphire’s Information page and I know that eternusamici has a shop
Do any of my followers have more resources for anon?