there is a big difference between a PAPR (Powered Air Purifying Respirator) and a SAR (Supplied Air Respirator. If you are going to spend money you want the SAR a PAPR is nothing more than a cartridge respirator with a pump.
to answer the original question the
Breathecool can be had for around $320
Hobby Air can be had for $400
(for half face models)
either will would work for limited duty as others have said a long hose is required (i recommend a 75' hose)