L2r is a 2xAA/14500 body, and takes P60/D26 dropins.
What drop-ins would be compatible depends entirely on what batteries you're running.
AA NiMH/NiCd -- You'll have 2.4V, so get a boost or buck/boost driver, the most common ones are rated for 0.8-4.2V
AA NiZn -- 3.2V, you might just make it with a very low Vf LED and DD, but the likely option is a buck/boost -- again, look for 0.8-4.2V
14500 LiFe -- 6.4V, anything designed for two 3V cells (6V) will likely work, definitely anything with a buck driver from 7.4V or higher maximum rating (3x 3V primaries/2x 3.7V rechargeables).
14500 LiCo -- 7.4V, anything designed for 7.4V or higher but not exceeding 1.5A draw from the batteries. This rules out high-current P7, MC-E, and SST-50/90 drop-ins.
Among the drop-ins that meet those voltage and current criteria for your battery selection, you can choose depending what color, how bright, and what beam pattern you want, but if you are running one of the low-voltage options, your choices are likely to be pretty slim.
How many modes do you want? 1 , 3 or 5 ? Low voltage (0.8-4.2V) for 2xAA. [FONT="]http://www.solarforce.hk/PRD/content.jsp?id=7.1&template=e.tmp.html
[/FONT][FONT="]I.[/FONT][FONT="]LC-1 (R2, single mode, 0.8V-4.2V) [/FONT][FONT="]- New!![/FONT] [FONT="]III.[/FONT][FONT="]LC-1 (R2m, 3 modes, 0.8V-4.2V) [/FONT][FONT="]- New!![/FONT] [FONT="]V.[/FONT][FONT="]LC-1 (R2m, 5 modes, 0.8V-4.2V) [/FONT][FONT="]- New!!
[/FONT]You can get them at ITC on Ebay or at sbflashlights and several other places.
I bought the 3 modes version, because I don't like strobes.