Alto/WAP is the best out there...you might not like the price! My pal Steve D'G searches worldwide for the finest tools in each category.....I bought one of these 14 years ago from Steve and its still going strong. One major feature is they are MUCH quieter than the shop vacs at Home Depot/Lowes.

http://www.ultimategarage.com/shop/index.php?cPath=899