I have a pattern for a string bikini top that could have a band added at the bottom, but it still will not have the support that any woman over a B cup would need for dancing.

Basically, you begin with a short chain, and increase at one end. You work one sc on one side of the chain, put 3 sc in the last chain and then work down the other side of the chain. Chain one and sc in each stitch till you get to the "top" of the previous row where you put the 3 sc. .....That doesn't make sense.

Chain 7. SC in 2nd chain from hook and in next 4 chain. 3 sc in last chain (increase!). Sc in back of loops in next 5 stitches. (5,3,5)
Row 2 .. Work back loop only from now on.... chain 1 (turning chain) sc in next 6 sitches, 3 sc in next stitch, sc in next 6 stitches. (6,3,6)

Keep up the idea till the cup is the right size. The shape will come. To finish, you attach your yarn to the top of the cup and make a chain long enough. For dancing, I would probably try to figure out spacing and make a band across the bottom. I'd use a piece of string or cotton yarn long enough to comfortably tie around the back. Tie it there! Hold the cups in place and mark the locations on the string. Untie and using the string as a guide; create ties and attach the band with sc across the bottoms of the cup. If you're only talking about an inch wide band, I'd do the whole length in sc (both loops). Treate the string like you would a measuring tape. Don't crochet with it.