I have two HKS aluminum flanges for sale; one is a clamp-on style (you have to use some 1" silicon hose to connect it to the piping) and one is weld-on. I got the clamp one from Ebay for $15, the weld-on was from Titan (I believe) and I paid $40 for it.

I'll let the clamp-on go for $10, and the weld-on for $30. I got a complete upper IC pipe with a flange already welded on from a 2GNT member so I don't need either one of these.