I bought ones for a Triumph Thruxton for my Calvin. They are for 41mm forks and ours are 45mm. I have not installed them yet but when I was researching before I found a post somewhere that said they work but just need to stretch a little bit more.
Part no. A9638018
These are the specs,
40mm INSIDE DIAMETER FOR THE FORK TUBE
LENGTH UN-STRETCHED / AT REST 150MM approx
LENGTH COMPRESSED 75mm
DIAMETER AT FORK LEG END IS 60mm UN-STRETCHED.