Good shapewear? Help please!

I got mine from Fredericks of Hollywood, and I really like it. It's a highwaisted brief with booty shorts. It makes me feel firm and smooth and I don't feel all scratchy from my dress. The only con is they're shorts. So my BM pointed out to me yesterday... "How the eff are you going to go pee?" I said "Well Darcey, you're going to have to help me!" lol. But then it got me thinking... I'm going to have to basically take my whole dress off! Anyone else know of any good shapewear? With a slip type, or maybe some buttons on the crotch like a onezie lol.