I lucked into a wide selection of dummy rounds when I was teaching hunter education in Saskatchewan. Ones and twos of the major cartridges, but not enough to load a mag. I think the provincial association had sweet talked one of the companies into swagging them. Haven't seen that kind of generousity agian.
Like the previous posters wrote, you can make them. I made some 7.62x39 dummies with spent cases, a screw threaded into the lead base of the bullet (trimmed for length) and epoxy. For visual ID I drilled some holes in the sidewalls. I tried just pulling the powder, but the bullets kept sliding into the case.