Sorry Bob I haven't got one but J Knibbs supplies repros http://www.airgunspares.com/ as also do
Protek Supplies http://www.proteksupplies.co.uk/bsa-spares.html
I have used a John Knibbs H section one and thought it was ok, Protek only supply the U section ones and I don't know how good they are.
atb
dogsbody