Max Cervantes worked on this prop and would probably be the best person to ask. He can be found on Facebook and a ton of Trek prop groups (no sure if he's a member here). What Max said about the tip of the ENT disruptor is that it's the same tip as the palm disruptor from ST5. "It was the flash suppressor from a Viet Nam era M16 sanded down at an angle." But I think he misspoke as the disruptor tip look more like a drill chuck or something. Below are some photos of the tip that was machined for a replica.
What's funny is the side hexagon shape that was mentioned above. The hex is the same style of the two hexagon "blinders" (Sonic Panels) the TOS disruptor has (which looks like a wall hanging from TOS as well).
This is the m16 tip used for the palm disruptor.
These two emitter tips are not the same as the palm disruptor. What I would like to see (and make for my collection) is not just an ENT disruptor, but the disruptor "rifle". It's an impractical design as where the fire button is at compared to the supposed telescoping stock (it never telescoped). I remember it being held like a pistol.