I am a bit confused as to what you are exactly trying to do :thinking:
The KX1 (& older KL1) are designed to run on 3v (single primary cell), while the KX2 (& newer KX2C) are designed to run on 6v (two primaries).
The E1L includes a KX1, but indeed has a lower MSRP than the KX1 alone. The E2L includes a KX2, and its MSRP is slightly higher than the KX2 alone.
The E1E/E2E bezel(s) are thread-compatible with all E-series battery tubes, but of course, are designed for an incandescent lamp. The lamp chosen will depend on the voltage supplied (3v, 6v, other?).
There are aftermarket drop-ins available for E-series bezels with various voltage requirements, output level(s), and tints. There are also alternate E-series compatible replacement heads, as well as aftermarket incandescent lamps (which may also permit different inputs and outputs).