A while ago, I hastily bought a Vivitar VI 6x7 conversion unit on eBay, in the hope of printing the occasional 6x7 negative in my collection. I buy "as is" obviously, and that time, it bit me back. When the unit arrived, I gave it a cursory look and stowed it away for a couple of weeks. Eventually, once I put it in the enlarger, I noticed that the condenser unit only had one lens. I thought nothing of it, until I realized that the light was not properly dispersed. I remembered condenser enlarger schemas: they always have two identical positive lenses placed convex-to-convex. The seller did his best to try to locate the missing lens, and after quite a few checks, nothing was found. I'm left with the following dilemma: either cry a little bit over the lost money, and save to find another 6x7 conversion unit; or try to find a way to add the missing condenser lens. Is there any hope? Are condenser lenses more or less standard between brands? Does anybody have a spare?