Does trijicon make a mount for a milled out slide? I cannot seem to find one....all ive found are the ones for mounting into the rear sight dovetail. I tried contacting trijicon but no response so far.

Springer Precision makes an adapter plate to mount various optics, including the RMR, onto the factory milling on a 320. Obviously the screw pattern would be the same as a 226RX but I'm not sure if the footprint is otherwise similar enough to use the adapter.