A little google-fu yielded this:
http://www.mcarterbrown.com/forums/1213324-post8.htmlI think the common name is 'high flow'(that's what mcmaster calls them). Body size is 1/8" NPT. Brand names: Foster - FST series, Parker - ST series, Dixon Perfecting - E series, Hansen - ST series.
When I built my booster, I bought all my HP fill stuff here www.scubacompressor.com. Not the cheapest, but they were reliable.