racer38 wrote:The disc is common with a Honda quad bike or something. I bought a new pattern one from the US for about £40 delivered last year. Same disc, same fitment. I'll check next time I'm sat I front of a PC.

It's a Honda CN250 scooter.

I think it's called the Lead in America. The Helix/Fusion in Europe/Japan.

Webike Japan do a few different versions. Inc' wavy Galfer and Braking ones.
I bought five of the plain standard shape aftermarket ones from them last year, made by Rise.

They're slightly larger in diameter, if I remember correctly, 189mm.
I'm going to get them turned down by my machinist.