You could use two of the $19.95 specials side by side, not inline, so each one would take 1/2 the air flow. They would last longer and not slow down the volume of air you need!
Have you check here(
http://www.tptools.com/ ) , they have a pretty good web site with usefull information. Also check with(
www.surpluscenter.com ), you never know what kind of good you might find. Joe