Jeff Erwin is right, Cumberlands (aka NW Trapper's supply), will have everything you will ever need for trapping. I do however suggest that you deal with them in person. I brought all my fur there for years when I lived a few minutes away from them. They can be very good or very rude about how they deal with ya. Russ, Rusty, and Jade are all nice guys, but they will try to get a few extra bucks if they can. May be different on just buying traps, but if you plan on trading furs for traps like I used to, you will get robbed. I was in high school and they didn't think I knew crap. However, my uncle worked with the North American Fur Auction, so I knew enough.....
They do have everything, just shop around for the best price.