Well, I am getting married when I go on my Grandeur cruise in may, and I had a heck of a time finding a low back or backless brathat was comfy and was not gonna cost me $50. But, I found a a backless bra that is super comfy at Bon-Macy's (formerly Bon-Marche) for about $28.
dont know if you have La Senza in america but they do a great range of products includint clear straps which you put onto the back of a normal bra to turn it int to a low back bra and it is only £5 and can be used on any bra. they also to a bra which is totally backless and just sticks to you with strong adhesive. I am a DD and although i havent worn this for a full evening yet whne i was practising it seemed to give me as much support as a strapless bra.
You can purchase wrap around straps from JP Penneys. They hook onto your favorite
bra, criss cross along your lower back, and hook together around your stomach. Very
comfortable, practical, and cheap. (about $8.00) They work great with low back dresses
that still have sleeves.
Are you looking for backless & strapless? I found one at either Dillards or Foleys around Christmas that fastened around the waist. I think it was around $25. It has "ribs" in the front to provide support. The straps can be removed or worn in different positions - depending on cut of the dress. The good news is it provided support (I'm a 36D so I need some support!), bad news is the ribs started to dig in after a couple of hours. They might have some similar or better ones now since it's prom season. I've tried those stick-on things - they're hard to get on straight, you still have that "jiggle" look, and they hurt like you know what to peel off! You might as well use that duct tape that I saw on someone's packing essentials list!
If you are a woman of petite endowments, I agree with deb - be free. I wish I could.