Another thought I had on this: blowgun
After college, I had a place close to downtown for 9 years, and had intermittent plagues of cockroaches. Some of them were pretty big. This was when I was starting to get into firearms and hunting. I acquired a couple of blowguns and my friends and I would sit around at night and pick off roaches on the wall. The projectiles were just sections of spring steel with a sharpened point, and we found we could pin a roach from across the room.
A similar rig might be just the thing for lizards.
