Slckshift Parts

try Fowler’s. https://www.fowlersparts.co.uk/

 

Why not fire off an email to triumph themselves?
Can't do any harm and they maybe able to get you some info as to where to buy too?

 

I assume this is for a pre-unit gearbox? T110? If so, I'd think you probably need to find a specialist supplier. Might be worth trying SRM as they do recondition pre-unit boxes and might be able to give you parts dimensions.

https://www.srmclassicbikes.com/make-and-model/pre-unit-triumph-twin

 

http://www.klempfsbritishparts.com/ https://morriesplacecycle.com/product/57-1536-lever-clutch-operating-slick-shift/ Two places worth trying as well as ACE in London.