Tank for XS650

It seems I put a technical question in the General forum. Will that matter much? Here's a repeat: I need a little guidance in how to find and fit a suitable tank for my XS cafe project. The bike has clip ons and I'm having a bit of time figuring out how to know which tank might be right for me,(the stock tank works, but I don't want its' weight or look) I see lots of lovely ones on the web, but how to tell if they would work? Any suggestions, leads, or hints would be greatly appreciated? Thanks a ton (up).
Jamie