I know how ya feel hun! I had the same problem, I couldnt find a good bra that would stay in place. Try: Le Mystere, Lilyette, or Jezebel, they have great shape to give you a little more tata & they are reasonably priced. Here's a link so you can see the ones Im talking about.

Strapless bras, Strapless bra at Bare Necessities

I've had luck with GapBody bras. Go and try on a bunch..

Thanks for your help!

I have a pretty small frame as well. I have had luck with Cosabella. They seem to be cut just a little smaller everywhere.

I looooooooove Body by Victoria strapless bras. They have an elastic at the bottom so it really stays put on you, even after a long sweaty night of dancing.

^ i agree with the above, I have the body strapless is every color and it really is a great strapless... only i don't think vs carries them anymore. i wanted to get another color & couldn't find them in the store. Maybe try in your area?

Unfortunately, I have one, and it gaps at the top of the cup when strapless. I'm just that tiny I guess!

Have you tried H&M bras? I admit I don't have a little chest but they have provided me tons of cleavage and support

I'm grad you brought this up. I have the same problem!

Same here. And the elastic gives me a bad rash.

I guess I need 30A...

agree with courtz, H&M has a lot of variety! I also recommend gap body too. i have a strapless and they work great.
But if worst comes worst, i suggest you look at the tween sections at target, mervyns, sears, limited too and such. they have a lot of bras in smaller sizes.

I actually searched both gottschalks and mervyns yesterday and found nothing that would work for me, it's kind of a small town and selection was sparse. When I visit my bf in sf next weekend hopefully I can check h&m!
Good news is I tried a VS secret embrace on today and it worked for me. The cups kind of seem to curve in on the top so there isn't the gapping problem. I'm still going to hunt around, but that's the best so far!