From Linksys on eBay... not sure how long it will last but pretty decent price. Just check on it once in a while as they refresh inventory.
http://www.ebay.com/itm/301783762809
Update: Bummer - Looks like the sale went from 29.99 to now $39.99.
Update 4-13-17: Seems to be moving up in price, just checked and now went from 39.99 to 49.99.