Irp, I believe any AA cell will work in the Key Lux, but I think lithium works best. I haven't yet done a runtime test with lithium or alkaline yet. A Ray-O-Vac iC3 NiMH lasted 2 hours 36 minutes constantly on before it started to blink, signaling a weak battery. One thing I noticed is that with an alkaline cell, it will start to blink when the cell weakens, and becomes a bit sensitive to being tapped. (If I tap the light, especially the tail, it will start blinking). The weaker the battery, the more sensitive it becomes. With a lithium cell, it wasn't as sensitive, and tended not to blink, but it dimmed instead.
I pretty much am going to use lithium cells in the Key Lux from now on. Besides the performance gains, I feel that a light that costs as much as this light does, should have a lithium battery in it to protect from the leakage that can come from alkalines.
I think you'll really like this light.
AtomicCandle, as far as finding an empty module, maybe you could email Chris at TnC. He might be able to help you.