You mean like this one?
This is designed for FS9, but you can paste it into FSX, and it is flyable (as you can see from this pic), but there will be no cockpit, I guess you could put a 2D download one in there for it if you wanted to though.
Search Avsim.com for this file: b-52_sp.zip
Shockwave make this which works in FSX. This is bloody brilliant incidentally. Trust me, you will love it. (you can get that paintscheme for it from Avsim, because it doesn't come with that paint job BTW, it's one of mine):
http://www.shockwaveproductions.com/store/wop2_b17/
There is this payware B-52 (for FS9) too:
http://www.alphasim3.com/store/produ...roducts_id=102

Chock