We find these on the back end cap in the DIY section at Wal-Mart, it seems like they are on permenent "Roll Back" at our store,
They are always less than $5, we do like them, esp with the lil kids, but we have found that if you leave batteries in it, they will corrode and distroy the contact points
our store also has just the mini fan fan with foam blades for like $2 year round