doesn't say they can't take em either....
Holdout does not have any mount points. But you can buy spare clip for them. And holsters. And.....
*Opens a cannister of IRL powder, and sprinkles generously*
A mount can be added to darn near anything, really, there just aren't rules for that level of gearheadedness.
You could realistically put a scope on a .25ACP pocket pistol, or a laser under the barrel, but It won't be a pocket pistol with all that stuff on it. Nor does it really make sense, but weapon mounts aren't magic, and don't require a lot of tech to add.
In fact, if you had more money than sense you could probably mount a laser on the bottom(s) of (a) magazine(s). If you reinforce the magazine catch, it may not even cause feed issues. But it's still silly.
Then there are side mounts, which are all the rage --
today -- but not in the game.