If I'm thinking of the right kind of skirt, Moondance carries them:
http://www.moondancebellydance.com/skirt.htm
They're just over halfway down the page. They call them: DOUBLE LAYER CHIFFON SKIRT MD121
A friend of mine has one of these. It has a wide black elastic at the waist (probably about two inches wide) that she has to hide under her hip scarf when she wears it, which is something you may want to bear in mind.