Hi Richard,
I bought a set of BKT tyres for my C8 last year, from Big tyres UK.
https://www.bigtyres.co.uk/
There is a whole thread on availabilty of 9.00x13 tyres
here
Good question about the canvas; Just like you I also heard that both Allied forces, as well as Worthing, only do US canvas projects.....but, I haven't asked them personally!
Good job on the C8!
Alex