Just to be clear: the plastic Bluemels fenders everyone's talking about here are not made of celluloid. Those early celluloid fenders (the ones on my Raleigh Clubman were made by Britannia, but Bluemels made some too, up to the mid-'50s, I think) were really brittle and hardly any of them exist anymore. Every once in a while you might see some on eBay (esp. eBay UK), but they'll probably be in sad shape and really expensive.

As for the more modern (i.e. '60s-'80s) plastic Bluemels: I might (might! not definitely!) have a lead on a pair of white ones. PM me if you're interested.