I would imagine that with the non standard swinging arm and the brake calliper mounting plate you will end up having to make one. I had to make two up for my bike, which would have been easy, except that I got it into my head that they should be 316 stainless steel and the only lump I could blag was 50mm; hard graft on a little lathe!
By the way CJ, did you used to live in Bristol many moons ago?