On Amazon right now you can get these awesome Pentel Hi-polymer Block Eraser, Large, 3 Pack, White (ZEH10BP3-K6) for just $2! These are by far the best erasers I have used, you can’t even tell something was written there after you erase with these.
These are part of Amazon’s Add-On Program and will ship free with a qualifying purchase.
Note: Amazon prices and promotions can change at any time. The price(s) listed in this post is/are subject to change.