Actually, another place to try is Cache. They are a tad pricey, but I'm on their mailing list and get $25/off coupons every now and then. I got a carwash skirt there, but unfortunately it's a size too big for me now. I usually have better luck with tops than bottoms there because usually by the time something goes on sale, all they have left are size 0's and 14's.
You can also try going into the junior section at Filenes or Macys. I see some tops and bottoms that seem like they'd be good for dancing, but they're not the best made garments.
Putting the word "dance" in front of clothing, unfortunately means adding another 25% or so to the price of a garment!