Anyone know how I can tell if an MS2000 Strobe is real or fake? Lot of replicas out there.

I do a little airsoft on the side.  I haven't seen any replicas that I've noticed.  I've got a few real MS-2000 strobes at home I'll have to see if I can get one of these replicas and compare them.  Not like there's much to them.  2 double a batteries, a sliding body that puts the blue filter infront of it and an IR cap.

I went through the same thought process over fake strobes and certain other gear.
Settled the matter by deciding to buy safety equipment and critically important things straight from authorized dealers and paying full bore prices.
You likely qualify for discounts anyway.
Other stuff I do sometimes buy on the used market, and if I am suspicious of it and contact the manufacturer, they usually always tell me what to look for, and I tell them who sold it to me if the seller is a large volume guy. KAC is the only firm that would say only that mine was fake, and only because I sourced it from a private party who is someone other than KAC (my KAC sight came with a rifle attached to it).

Even a used genuine strobe is more likely, even after a pre-mission test shows it works, to operate intermittently or fail when in use, and you must dismount it to check. Too risky for my purposes.

The genuine ones seem inexpensive enough - I purchased six of them off the EE several years ago.   It doesn’t seem that there would be fake models of such an inexpensive item.  I’m recalling $20-30 each.  I’m certain they were authentic.

New real ones are in the 100-150 dollar range, which surprises me considering how they're built which isn't all that complex.  I used to work in an MOS that maintained them (basically consisted of switching out the batteries and making sure that there were no light leaks with the IR shield up) and they felt pretty flimsy overall.  The battery compartment had a threaded insert that would pretty easily pull out of the body making the light un-serviceable.  I scored a few that way since they were going in the garbage anyway and just epoxied the insert back in.  Not an approved repair so no way I was signing off on it going back in a survival vest but in the back of my car in a get home bag sure thing.   The blue filter would regularly be pulled down and not be fully functional without coaxing it back out with a pair of tweezers without ripping it out on accident.