I can't remember how the detent system on the neutered bayo guns, (was it Navy Arms that did that?), that had the spring-loaded detent setup to keep the cleaning rods in, was constructed. Was it simply a ball-bearing and a spring, pinged to keep it in? Or, did it use a hardened "plunger" of sorts with the spring? I don't know if it would help a lot of owners, but it definitely would help the ones that have the rifles like the OP.
I don't have a drill press set up right now or I'd go out and fiddle my way through it. I'm sure someone with access to an original detent system and a few tools could figure out the drill bit sizes, ball bearing size or plunger, (which could probably be sourced from some already-manufactured parts from hardware stores or gun parts suppliers.) If one would take the time, a list of parts and instructions could "probably" be easily drawn up for future owners to use.
Just a thought...