When you say you had no luck at your local hobby shop, Michael's and HobbyLobby, do you mean they had no snap-together kits at all, or they had some but they were more expensive than you're looking to buy?
I'l second those who have suggested eBay. Also, if you can get to shows, check among the vendors. The old Monogram snap-together aircraft kits aren't bad, if you're looking for something to practice on.
What do you want to practice, too? Finishing techniques, or all-around modeling techniques, from pre-assembly to a final sealer coat? Either way, you might as well just look for cheap glue-together kits, because you'll probably find more selections, than if you restrict your search to snap-together.