I'm also looking for one of these handles, specifically the right-handed one with the raised thumb-button, as used on Sarge.
Kev, or anyone, if you have a spare handle for sale, with the Sarge style thumb button, I'd be interested in just the handle and button (and trigger.)
Heck, I'd even buy a left handed one just to get the thumb button.
I believe this was a standard Suzo Happ part used on many games: Spy Hunter, Sarge, T-Mek, Special Criminal Investigation, etc. but the trigger and thumb button varied depending on the game.