You generally have to look for these at speciality places, or from the factory (if they still make them.) Except for 10-22 magazines and Ruger and Buckmark pistol mags, most gunstores wont' stock them.
I had to find an even more obscure magazine, and did a websearch. Which was difficult enough, because I kept getting the names of publications.
Finally, I found two sources that sell magazines for firearms. Can't remember who they were, but they're on the Web.
Good luck.
