Botach via eBay offers the Wenzel Beachcomber Backpack in Grey/Black for $14.99 with free shipping. That's $30 off list and the lowest price we could find. It features:
padded back panel
ventilated shoulder straps
MP3 player pocket
flap closure w/ buckled compression strap
There are many ways to get cheap and even free services and goods after reaching a certain age.