I don't think you can buy them in a regular retail store anymore but the Ab-Slide works great. It's blue and you roll it out in front of you on the floor and then roll it back. You might find one on Ebay or Craiglist or a thrift store. It doesn' work in a week but in 4-6 weeks you will have a great tummy.**warning**: it does work but the instructions say to use for 3-5 minutes the first time you use it--if your abs are really flabby only use for a minute or you will get so sore it will be hard to breath.
You can get Shapeware that is like a wide band with boning and hook and eye closers that goes from about the bottom of your bra to your belly button. It will suck you in nicely but not be real noticable or uncomfortable. If your dress is real sheer or clingy opt for a skin toned one and put the hooks either in the back or on one side whichever looks best.