You have two "easy" options:
1) Fit the LED in the tail cap :lolsign:
2) Find a driver that must be fitted in series with the LED (a resistor is the simplest of this, but there are other options). Only ones that I know of at the moment are not efficient at all.
With most of the advertised drivers where you need two contacts in and two out with at most one of them common, it will need some wires.