Like that one foldsinhalf- something like that, or Jur's mod for his Swift, would be perfect, certainly in terms of price (!). I'm going to pop in my LBS at the weekend, they might be able to do something like that. FD would be neater and tidier, not necessarily better at sorting the problem.
fmattheus- I had looked at those kind of things, MTB bash guards, etc. Either ££££ as in the case of the Rohloff (which cannot fit my seatpost, btw), not available in the UK (and expensive to import), not practicable (due to either the chainring size or the seatpost diameter), or no better than the cheaper options like Dahon's own little plastic doodad. Which doesn't work. Jay Gaerlan sold me a rollerkit (and he knows Dahons)- couldn't fit the right way up, and where it was mounted was no help.