Briley or TruLock should have them.
JR
Some reason Colonial chokes pop into my head...did they make thin wall chokes at one time ?
I think you are right. Mike Orlen will install them on a gun if the barrel diameter is large enough. I sent him a gun and asked him to either install the thinwall tubes or open the fixed chokes. I had measured the barrels and they were right at the minimum diameter, so Mike would not risk it and just opened them up.
I think that Brileys will install their tubes on almost any gun.