I have recently been having a wonderful time shooting with my father's 45 year old Contaflex lV

It has the standard 50mm 2.8 Zeiss lens. I am interested in getting other lenses for it (115mm or 35mm).

My question is where?

Camera Traders (www.cameratraders.com) seems to have a few in stock.

Has anyone ever dealt with them before?

Any other suggestions as to where I should look?

Thanks