Almost impossible. Not manufactured since the 1970s. Try boatsandoutboards.co.uk (or a google search, or have you done that?), but this is going to be difficult
The driveshaft is a standard dia, so you might be able to get a merc/OMC/yamaha one to fit, maybe with a bit of trimming?
Try Starrey Marine, they are either in devon or cornwall, but they were the sole importers abouts 18 months or so ago, sorry did have the address, but lost it
There was a bloke called Bill Higham Marine up north somewhere did VP outboard spares. He advertised in Exchange & Mart. Also listed in an old MBM which did a listing of old outboard spares - you could try them.
Best of luck