Update
Updating database... Please wait.
Saturday 5 May 2018 at 05:17
Quoted from EM-PINMAN:PBR sells the 2 wire Interlock Switch if you wish to install a new one, just make sure you have the proper bracket that holds it in place.
Well the one it came with looks like it's in good shape -- I just hadn't come across it yet in the hobby and wasn't sure what to do with it...
Source: http://pinside.com/pinball/forum/topic/kill-switch-on-a-gtb-how-to-room#post-4380322