You just have to keep checking gunshops and online auctions. For one in decent condition you will pay at minimum $300, on up to over $500 for a nice unit.
I got lucky and bought one for $299 at Gandermountain in Johnstown PA on X-mas Eve last year. Its in [censored] fine condition, made in 1941, and came with original box and manual.
What you may want to do is, make a wishlist and pass them out to the FFL's in your area. Let them know you are looking for one if they happen to be offered one in trade. Note on the paper the all the details you are looking for, like; condition, serial # range, barrel length, etc, etc. That way they might be more likely to take in as trade knowing you will buy it. Just about all the storefront FFL's for in a 80 mile radius has a wishlist from me that I update once every 2-6 months depending on if I score on something. ..its helped me gain a few guns I was looking for.
ok thanks i'll have to check this site out then...I may be looking for some really cheap guns in the next couple of months like $50-$100 cheap i'm going to be starting gun smithing courses and i figure i'll need some guns to works on so if anyone sees any please let me know(as long as they're not in terrible condition) thanks.