I recently purchased sleeves off of eBay. I got an 800 pack of black BCW brand sleeves. They are cheaper than Ultra Pro's and seem about the same quality. I'll let you know after playing with them how they feel.

The 800 amount is more than needed, so I'll have extras. I've already started to sleeve and tweak the cube a bit while doing so.

Sleeves Sale linked here
Sleeves Seller linked here