The easiest way is to buy a surefire host like a regular C2, 6P, E2E, incandescent versions. Then just buy the IMR Light assemblies from Lumen Factory website along with the 2 16340 IMR cells. Pop those items in your host, you will get a small pocket hot wire light. About 270ish OTF lumen for the E2E and 350ish OTF lumen for the P60 modules. The is about the best you can do with the smallest bodies and the easiest.
About using LED for a pocket rocket is an oxymoron to me. As either the cells or battery with drop out of regulation after a few minutes of use. The cells will sag as you draw high current too. The other problem associating with high power LED emitter in a small body it will cook itself up inside the pill. A lot of time either the pills are made out of brass or they don't have good thermal path for them.
There are reasons why modders like Milky, DaFABRICATA, Dark Zero, wquiles are very love here. As they will make a proper heat sink that mates to the body properly. Contact these modders if you want a host modded. I have seen excellent work, and their mods are extremely clean. :thumbsup:
There are stock models out there that some CPF members offers that suits your needs. For example Mac builds this 18650 Ti SST50 light, Download offers a highly modified 18650 again SST50 emitter light, andElektroLumens offers a direct driver 18650 MC-E emitter light. These 3 are the only models I know of that are offered on CPF here. If you dig around probably there are more so call "pocket rocket" out there. I have to tell you this though, the biggest limiting factor are the cells themselves. Don't expect too much out of a small package is all I can say.