Is it just the plastic cover that has got brittle and is falling apart rather than the entire light unit? If so it will probably be cheaper to get hold of a second hand cover. Plus it would save faffing about with the wiring.
Also worth posting in the 'wanted' forum here as someone may have one. I might have one lurking in the garage somewhere so will have a look if you don't mind waiting a week or two (I won't get the chance to look for a while!)
Yes it is just the cover... but actually it is only a cover anyway isn't it? I mean the plastic cover contains all the metal bits and just screws onto the wood, there is not supposed to be a base is there? If so mine is missing!