Oooh if only htis had been a few days sooner. They were running a maternity clothes co-op on another forum I'm on and they had up to 3X. Though depending on what I get I may have some I can't use/won't wear that I may be able to pass on as I'm due in early December.
Do you have a Motherhood outlet near you? They carry up to 3X there
Also try a bella band (you might have to order online I think target only carries up to a L in stores), but it let me wear my snug pants for the first few months, I could probably wear them still but I'd be doing a lot of hiking them up. The L/XL is supposed to be for size 20+ (I wear an 18/20 and bought a Med/Large and it fits over my belly still)
Linky to Target.com