You wont find them, as far as I can tell. I have a TT double too, and take a keen interest in T Turner products when they come up for sale. I emailed the Thomas Turner gunshop in Reading, UK and they said maybe they could help but never came back with anything.

What have you got? Is it the TT double in .500/450 2 3/4" that was on Gunbroker about 4 years ago?