zennco yb125 supermoto, problems with rear sprocket?

I've had my bike since June this year, and MOT came about end of September. A few little problems, but main was that the rear sprocket was worn down. On my particular model, it is spaced out in the middle so it clears the rear tyre. It also has a weird bolt pattern. After looking around on the internet, I can't seem to find a replacement, so my question to you guys is: do you know of any places in the UK (preferably Essex area) that can make custom rear sprockets? All help would be appreciated :)

I am convinced that any machine shop that has lathe and milling cutter, can make for you sprocket that you need.