Hi
Have you tried BSA Owners Group (http://www.bsaog.co.uk)?
If you are really stuck, I have one as part of a Rifle/Scope/Bottle combo that I would not split
I did have one for a Rapid7 as a spare but sold that to a Rapid man, they are fine too!
Pardon my pre-Xmas joke!
ATVB
David