Nothing flashy, but cheap is good, as it would be to replace the one that got nicked out my daughter's bike last week...

ideally 400mm, but 350m would probably be enough.

if only it was 27.2 - got loads of them knocking round, so happy to swap if anyone is in need of something of that flavour

I might have one. Message me if you don't get sorted as I'll have to dig it out