I just wear little boy shorts - I get them in the women's department, but like at Target or Old Navy, etc. Just bottoms that are tight-fitting shorts that you would wear to bed in the summer. The lingerie dept is a great place to look. To this day, my favorite pair is a pair of mens boxers, size small, all cotton, ecru. I don't think they make them anymore, and I am so bummed.
Anyway, the shorts are nice and low and go underneath of my belly, or I fold them down so that they are under my belly and then I put on a sports bra and I'm good to go. If I'm doing something outside that requires more cover, I buy pants a size larger, make sure the pants are under my belly, and then put on a zipup or something over the top to make sure my belly doesn't peak out anywhere.