Most anything of this sort that I need, I can find at my neighborhood hardware stores. For items they don't have, in town there are three shops that specialize in compressors, hoses, clamps, fittings, adaptors and such. Depending on your location, check the phone book for specialty shops like that.
I find it helpful to take the items along, so the shop can see exactly what it is you need. They can always simplify anything I might end up with, if I do it myself. I've created some real Frankenstein devices in the past.