I currently use the EfficientVelo mirror that Leisesturm linked and am happy with it. I didn't use the zip ties either, went with super strong double-sided tape stuff. It is a huge mirror (for something mounted that close in) but you don't notice it and what I like about it is that it can be positioned to "clear your shoulder" when you're in your riding position. I have the same flexibility issues as the OP and cannot effectively look over my shoulder. It's not convex, so the image in mirror doesn't get lost after fifty feet back as the German mirror did.