Hi Brendan
Try
Stellar Technologies in the US.
Note the following from the ST site:
“Wide-field adapters must be specially designed to guarantee that infinity focus will be reached on the camera chip. This requires that the backfocus distance of the lenses and the backfocus distance of the particular camera be taken into consideration in the design of the adapter”.
Cheers
Dennis
PS – if you want one urgently, I have one that you can borrow until you can buy one