Welcome to CPF.
The G3 uses the same lamps that work in a 9P or equivalent..
LF D26 ES-9:
LF D26 SR-9:
LF D26 HO-9:
LF D26 EO-9:
SF P90:
SF P91:
G&P G90:
G&P D26 7.4V "DX 10W xenon":
G&P D26 7.4V "DX 15W xenon":
Pathfinder P90:
WE D26 9V:
Pila GL3 LA:
all of those lamps should fit and work fine in the 9P and G3. If you are looking for the brightest options, the P91 and EO-9 are the best, with the EO-9 being the better bang-for-buck in that it will give about 35 minutes runtime and be almost as bright as a P91, which can kill a set of CR123s is around 20 minutes.