You might try a tri-suit from a place like Desoto Sports:
http://www.desotosport.com/products/racing.asp
I wear one of these and it fits comfortably. In general these kinds of garments fit fairly snugly, and I've found one or two from other companies with unfortunately placed seams.
Other vendors make them as well, and there are plenty of online tri shops (even a recent thread here on them).