I wants a mirror that's compact and I've seen on the other forums people like the top tube mounting type mirrors. But from the look of them they're not designed for folding bike frames such as Dahons that have massively oversized tubes. Do you know any brand that fits / a mod solution that's clean?
If you cannot find what you are looking for, consider this. I went with the bar end Mirrorcycle unit. It swivels easily on the upper joint in and over the handgrip, and nests just fine when folded. I carved a little mark on the joint to ensure repeatable placement when I unfold it. It is very stable and has moved in and out sometimes twice daily for weeks without requiring any hardware adjustments.