You might try contacting this company, they are the ones that manufactured and certified my larger tank...
Silvan Industries
And here is the parts list for my larger tank with the replacement parts numbers, this is for a 10 gallon SpeedAire tank, I suspect they would be pretty universal as it's likely they use over the counter clamps... Also supported if you Google up the part number (PT380200AV) for the clamp and it hits for Campbell-Hausfeld tanks, at about $50 a pop!
Grainger]Repair Parts : Grainger Industrial Supply