They're all over if you look around, J&G Sales has some really good deals right now ($80): http://www.jgsales.com/product_info....aa9be8233ad113
(gotta pay shipping/FFL, but they're still pretty cheap).
AIMsurplus.com usually has them pretty cheap, and you can also sometimes find them locally for alright deals (Bullseye in Lville usually has a few crates of them, or at least they did a while back when I was there). You can also pay $30 to get a Curio and Relic license from the ATF and then get dealer access to places like Century Firearms for even cheaper deals.
Be sure to check out www.7.62x54r.net (and their forums) for tons of info about them as well, these guns have tons of really interesting history behind them.
Ammo is also pretty low for these things right now too which is great (440 round can of surplus ammo for like $80 or so). Out of every gun I have, my Mosin's are always the most entertaining and fun overall (esp if you shoot them at an indoor range, everyone in the place will run over to see what the noise/flash is about). Shooting M44's with the bayonet out always gets fun looks too.