I know exactly what you mean, since I’m trying to get the same aluminium trim with piping for my Bedford CA Workobus (http://tinyurl.com/3zfajg)
It’s an aluminium extrusion about 9 mm wide, semi-oval in section, with a blue (in my case) rubber insert in the middle.
I’ve tried Adrian Bailey Classics, Woollies of Peterborough and contacted Dormobile directly — but to no avail.
I’ll post here if I find any. If anyone else knows where to get it, please let us know!
Otherwise I’ll be forced to “fake it” with chrome strip and vinyl tape.
Colin