Well, I really wasn't prepared for them not having the single available. Now I feel like I owe you something. Hmm.
Well, Six13 aren't the only a cappella Hanukkah singers. Here's a group that doesn't get the headlines like Six13, but I've always liked their stuff. Shir Soul's annual Christmas song features a medley of several Hanukkah tunes, all centered around a game of "Dreidel". And you CAN get their single at Amazon. Also at iTunes and CD Baby.