All I can tell you is what is working for me.
I found these 3A High Current Flashlight Tailcap Clicky Tactical Switch (Momentary Activation) to fit and work quite well in my “roll-of-coins” EDCs. They’re the ‘’S5 Clones’’ I mentioned earlier. They replaced the original Momentary OFF switches ~perfectly in size.
They should also work in the “normal” 501B’s I use which means they’d work in the old C8’s as well. Well… except for having to solder them in, which can be a pain sometimes.
HTH…