Where's the cheapest place I can find an air tank for an onboard air setup? I'd like possibly a 2.5 gallon tank with at least 3 ports (one being on the bottom). I've searched ebaymotors and other websites, but curious to know if anyone knows where I can find one.

 

Is their a semi truck wrecking yard any where near you? I don't have a OBA setup (yet) but this is where I am planning on going when money allows.