Catriona, a friend of mine had a 143 Ruby that she was trying to get rid of a while ago. I don't know if she put it on eBay or what, but I can ask if you'd be interested in a 143.

BTW, don't believe the "aero" vs. "upright" thing. For me, I erred on the size of smaller at first, since I was kind of between measurements and wanted to race. It was bad. Now that I have full support for my sit bones, I am happy. For crit racing, i tend to put the nose of the saddle down a smidgen to make it more comfortable when I'm in the drops for long periods. When I'm tucked forward, it's even more important that my butt is supported and not my soft tissue. So, if you've been happy with a 155, maybe you should stick with a 155 (or at least just take a 143 for a test ride before buying).