anybody know where I can find a replacement drive side (left) engine block as mine has smashed after the chain snapped. see photo

You'll probably have to get a pair of cases or that might be repairable Where are you?

Spotted one yesterday on us ebay,
think seller was guzzitech.

UK ? USA? AUS?

is that the only problem, and is it still in the bike? If so, repair it - cut/bend a piece of AL to fit the hole as best as you can, clean everything real well with lots of solvent, then sand/file everything nearby so that there is fresh, rough metal everywhere glue might end up. Glue in place with a good 24 hr epoxy - I've used MarineTex, PC7, and JB Weld all with good luck. If needed, build up a solid layer on top of the AL you cut to fit as thick as the original casting or thicker so the cover can seat - you can do this with more regular epoxy or you can use epoxy putty. Let sit for 2-3 days, then flat file the sealing surface down to the same level as the original machine work or even a little lower - you don't want the compressive forces of the cover working to break the epoxy bond. Seal it with a little silicon when you reassemble.

I've fixed much worse, and never had a repair like this fail, as long as proper attention is paid to the prep work.

Sam