We make our primers with a piston air compressor driven by a small gas engine, and small air tank for a buffer.

Currently we have three, using the cheapest compressor pump and smallest Predator engine from HF, around $250 parts for each.  Occasionally we'll screw up and let one flood in the river, like we did last fall.  After tinkering and cleaning for an hour or so, I had it running good again, but if not, back to HF...