Overstock has the Wet/Dry 12V Auto Vacuum shop vac for $10. I doubt it's very powerful but for the price, how can you go wrong? It includes an attachment to inflate mattreses as well. Shipping is $1, and it's included in the price.

http://www.overstock.com/cgi-bin/d2.cgi?PAGE=PROFRAME&PROD_ID=178778&siteID=NKa3hZy YoHA-_bOI7XUao8eGaCOIDiCHaw