Ive just always used the cheddar cheese I get at Sams club. I use 10% by weight and cut it into 1/4" cubes. You have to be careful with your temps though, if you can't keep your smoker below 170F, get the high temp cheese like br1006 suggested.
Allied Kenco Supply company (45 north)now carries High Temp Cheese, It holds up better and also has that eye appeal. I have used regular cubed cheddar and the flavoring is there but not the appeal if it melts into the meat.
I think it's under sausage seasonings or search bar for High temp cheese 10# or more it's only $4.50 per lb.
I just got some in for our camp. Let me Knoe if you still can't find it I'll give you the Number