I race a 500 Nourish triumph, as far as I know the shells are from a Norton Commando as Dave nourish told me once, as is the oil pump too..
Indeed Obsoletebikeparts has some old stock.
The new owner of Nourish engineering , Chris Bushell , is indeed a scam artist. He let people pay great deposits and didn't deliver anything. As far as i know he is bankrupt so it is difficult to get original parts. I don't know where his stock of parts is left , it was a lot !