I'd probably look at a dead nomad XC LTi and put a brake end cap on it. The Nomax 33 is the bigger 338 version that might have less back pressure and more durability but it actually tested louder on a 20" 308 than the 30 cal XC LTi in the '24 tbac summit.
TBAC is seldom a bad answer though.. A Magnus RR would be nice but they are freakin expensive and people are replacing the factory brakes with aftermarket ones anyway which just adds more $.