Ponz,
Might be hard to find, doesn't go bad so selling replacements isn't cost effective. I've seen another type of air filter on Yong Hengs, I'd just use that. EBay, search, "Yong Heng Air Intake Filter," you'll see an ad a few spaces down called, "5pcs. Yong Heng PCP Compressor Air Filter." Black plastic frame, white filter element, 40.4mm long x 15mm wide. ($15 for 5) WM