If it is going under a tux, it has to be thin and small. Walther PP series were DA/SA pistols, with a slide safety, in .380.
I'd think a Kahr P9-2 would be a good pistol to use. 9mm instead of .380. Consistent trigger pull. No safeties to worry about. [of course, nothing to 'snick' off to show he is getting serious.] same capacity- 7 or 8 rounds.
I had a K9 pistol and shot it on same day was shooting grandma's PPK.
The K9 kicked a LOT less, and was more accurate. The PPK was unpleasant to shoot, moved a lot, and was less controllable for me.
Of course, now we have the Hellcat, and others of similar size.
However, we need to remember it has to be Tux friendly- not too thick and bulky.
That leaves out most Glocks, in my experiences. Maybe that also leaves out all 9mms due to slide thickness.
He usually picks up a heavier gun when in combat insertions. I think it was a SigSauer I saw in his hand at one point, but I don't remember if that was what he carried or picked up off a dead bad guy [he did that a lot].