Not the tightening clamp but I'm looking for the exact same kind of clamp that most red reflectors are mounted on. I want to mount a light under my seat post and in fact I did mount one but the clamp is more suited to a 27mm seat post. It's a little short and I'm a lot ingenious but I want to do it the right way.

Where can I get such a clamp that fits the Dahon seat post perfectly?

Bear in mind I live in Japan at a US military base and can't just run down the street to the local store. I'll have to pick this up off the internet.