powered respirator recommendation?

What is the least expensive and decent full face powered respirator (i.e. dust mask with a fan to draw air)?
The reason I want a PAPR is because wearing an unpowered dust mask makes my face hot and sweaty. It also fogs up my goggle if I am wearing one.
The one I found most commonly listed in "froogle" is a trend airshield that sells for $300. Isn't there something less expensive and works?
Or perhaps someone has a plan to make one? Surely the materials don't add up to $50 (air filter, some plastic shield, a fan).
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I bought a Bullard PA20 on eBay for cheap. It has the belt pack for the battery and filter. It works well. http://www.millersafetyproducts.com/GroupInfo/GroupID/5536 The listed price will make you gag. I figure it's the lawyers whinging about safety product liability driving the price up. I got mine for around 200 bucks. New, and with an extra hood.
R
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