Sorry, this kinda seems silly to me as well.
But to answer your question-
I'm not aware of any light that "snaps" on. Most lights "slide" on and are tightened. The TLR-1 is pretty easy to take on/off in under 4 seconds. Can't vouch for other lights...
Gen4 G21: with TLR-1 and Trijicon night sights
".45 auto, because shooting twice is silly"