I am in the same boat, and still looking. You can finds loads on Ebay but most are potty. The main players are jetmac systems from County Down, and "musthave it".
Trouble is, some are buy-it-now, some for auction, some are honda&interpump and some anonymous far eastern, some are plus vat & some inclusive, some carriage paid and some £55 or £60 +vat carriage. Confusing or what?
If you want to drive a whirlaway or similar with it I should think a minimum of 300psi and 16lpm flow rate is needed. What does anyone else use?