I imagine you've already seen this.....but if not.....
Other HPA sources I've used were a Shoebox F10 (x4 or 5 years) and a Yong Heng (x7 months). Sold the F10 as a parts donor when I got frustrated trying to source replacement parts and the Yong Heng is still ticking just fine, with the caveat that the oil gets REALLY dark REALLY quick (impending...
www.airgunnation.com
I'm using a California Air Tools, 20 gallon, 5.3cfm @ 90psi compressor. The model # is 20020. Look's like they're running about $500 on Amazon right now. I think I paid around $300 for an almost new one from my local craigslist. Lots of compressors on craiglist or facebook martkeplace usually, some are worn out crap, some are barely used.
I highly recommend the California Air Tools brand. The big pro for the CAT compressors is that they're much quieter than comparable compressors from other manufacturers. I've also got a little 5 gallon Dewalt pancake compressor that I think is rated about...