I have an update for this question.
Hornadys use the same size as the Forster and Redding, which is 3/16". RCBS uses a 5/32" diameter. I'm not sure about Lyman.
Also, after a recent whizzin' match I remembered an experiment I had thought about years ago. Would you be able to use the case length gauges from the Lee trimmer sets in a regular case trimmer?
I had measured the diameter of a Lee gauge and found it was just a hair too big for my Forster trimmer and thought the answer was "no, not without altering it". Actually I have a ton of those Lee trimmers, because they are useful for other things, but the only one I use as intended is for the .41 Colt. I looked at the slit in the shank and a little bulb came on, with a little force you can get it started in a 3/16" hole, twist it in place and tighten the set screw. I can't guarantee how well the screw threads will hold up on the gauge, so use your own discretion.
Now I just need to see if there is a collet that will take the .41 Colt case.