Wow! That looks an awful lot like the 200cc MKII SS that I got. In fact, yours looks a lot better than mine did. My engine was stuck too, totally, had to hammer the rusted crankshaft out of the crankcase. But, I was able to find most parts from Richard, and from ebay. Keep your eyes open, the ebayers seem to post parts when they know someone is interested.
Otherwise, I have some 175cc case parts that I got from Richard, but didn't need to use. Contact me if you want to see exactly what I have to offer.
Gary