Hi Paul,
Clutch master cylinder (handlebar end) is Brembo PS15, same as the brake master cyllinder, so for both you need Brembo seal kit 110273920.
Same parts were used on MotoGuzzi, Ducati, Laverda, BMW etc, so google it and you can buy from your preferred supplier.
For me, Pre-Covid, I would ride down to Slater Laverda to buy them and have a chat about Hesketh, Laverda etc, but online I would probaby used Gutsibits.
The rear brake master cylinder is Brembo PS12 which needs Brembo seal kit 110279720.
Hope that helps,
Dave H