I think the SolarForce modules will for sure work in the G2 and maybe the M3. You can find them here, use the drop down menu to see all the catagories:
http://www.solarforce-sales.com/product.php?t=RB
Here is a cut/paste regarding them:
Examples of flashlight hosts that these Light Modules will fit:
Solarforce L2 series (L2P, L2X, etc), SF6, SF9, SF12,
Surefire 3P, 3R, 6, 6P, 6PD, 6PL, 6R, 6Z, 7Z, 9P, 9Z, C2, C3, D2, D3, G2, G2L, G2Z, G3, G3L, GZ2, M2,Z2, Z3,+ other Weaponlight models,
Blackhawk Falcata,
Boker B0006,
Brinkman Legend,
Maxfire (LX models on both),
Cabela's XPG (Xenon models),
Dereelight CL1H (all Versions),
DealExtreme {DX} HF-19, SKUs' ~ 1284, 4226, 14329, 14597, 14902, 15159 (DIY chassis), 15565, 15561 & OEMs, G&P T6, T9, T12, R12,
Hellfighter X-4, X-8,
Huntlight FT-01PJ, FT-01X SE (Luxeon versions on both),
Kaidomain KD Tough, & OEMs,
Leupold MX series w/ MX-100 bezel, M812, Mega CREE Q2,
Nextorch (various models),
Pelican M6 (newer version M6)...Slight modifications needed,
PentagonLight X1, Xenon chassis {to be confirmed},
Pila GL2/3/4,
Romisen RC-E4, RC-M4, RX-A,
Smartfire A-1,T1,
Spiderfire Q5, R2, X-O3,
Superfire C1, see Ultrafire models, Tactical Operations Products Stryker (slight modification necessary), Xenon models,
Trustfire T1-Q5, TR-B1/2/3, TR-C1 & 2, TR-C6, TR-Q5, TR-Q8, TR-C2
Ultrafire6P, 9P, 12P, C1, Alpha-C1, L2, SG.DX-B, WF-501A/B/C/D, WF-502B/C/D, WF-503B/C + extension option, 504B
UniqueFire L2, R5
Vital Gear F2
Wolf-Eyes (See dimensions), XLight HA-III Cree Q3 kit, HA-III Cree Q5 XTAR P4
XLight HA-III Cree Q3 kit, HA-III Cree Q5, HA-III 14500
XTAR P4
Other Custom & mod designs: The Boker BO006, Pelican M6, Pentagon Light X1 & Tactical Operations Products Stryker all need modifications to work as P60 host.
Courtesy of CPF P60 thread by "Orbital"
