Edit: Looks like Ernst and I were typing at the same time.
Most weapon lights are going to be made in china. That much is probably going to largely be unavoidable. Unfortunately.
The GG&G mount is what I'd pick. And is set up so that the thumb on your left hand can engage the switch, if you're using a traditional style light. Regardless, you're going to need the mount. I'm not sure if you can find it perhaps less expensive anywhere else. I'm only linking it so you know what I'm referring to.
https://www.swfa.com/gg-g-mossberg-930-flashlight-mount-1.html
In no particular order, surefire, streamlight, a lot of folks like Olight.
A lot can be said for lumens. There are many that like to have a light brighter than the surface of the sun and hot enough to melt a bad guys face like the nazi at the end of Raiders of the Lost Ark. But, I have found that a light too bright, not only hurts the "night/low light vision of a bad guy who may be looking in the general direction of it, but it also hurts yours to a certain extent too. Especially if you are needing to cycle it on/off. So that's going to be a subject you'll want to look into for yourself. Typically, 60-120 lumens is MORE than enough for a close range weapon. It gives you plenty of light to identify the target without destroying your night eyes.
And the reason why I like a weapon light over a laser is in the close proximity that you'd be using it indoors, that light beam is going to be pretty tight/small. Meaning, if it's on when you're pointing that shotgun at someone within close distance of you, whatever is illuminated is going to be hit if you have to defend yourself.
Lasers makes a small dot (or other shape), but does nothing to be bright enough to be able to actually identify what/who you're shooting at. While a light will do both at fairly close distance. I could get into more about why I don't like lasers, but it has to do with zero'ing them at the distance you're shooting versus how that will affect the pattern at real world distances because if you are farther or closer than the distance you zero it, that laser is no longer going to be zero'd.
I particularly like a light that has a constant on "clicky" tail switch. But that is just my personal preference. There are many available that has a "squeeze pad" that you can attach to the handguard that would work well too. Since shotguns have a lot of recoil, I don't like the switches that rotate to turn on (like some lights use) because under a lot of recoil, the switch may be shaken so much that it turns itself off.
I'm going to be perfectly honest with you and everyone here. My favorite bump in the night weapon lights are nothing more than Ray-O-Vac "indestructible" work lights that run on AA batteries. The lights themselves have worked for years. They're cheap. And you don't have to stock a bunch of oddball sized batteries. And to take it a step further, I even use rechargeable AA batteries in mine.
So, it's all in what you want to do.
I know that my lights are going to come on when I push the switch. They're ~120 lumens or 60 lumens on low. I have the option of barely pressing the switch for a momentary on/off or clicking the switch to leave it on in for extended periods of time so my fingers don't cramp and feel like they're going to fall off if I have to cover someone for a long time.
Example:
That is what I use personally. I have some lights that I've paid more money for, but these are my work horses.
