I've pondered this for some time, and the best I can come up with is to make your own attachment point and place it between the light and the momentary switch, sort of like how the Moddo clips fit on. What you need is a small, thin washer with a small loop attached to the outer rim, with that small loop acting as the either the keyring attachment point or for a split ring which you'd then attach to the keys.
Instead of a washer you might just try a small loop of wire under the momentary switch, and leave a little loop that extends out a bit.
Of course the trick, as I understand it, would then be to make sure the momentary switch still worked correctly (because the washer adds a bit of thickness and places the momentary switch farther out), which might mean extending the contact tip a bit, possibly with a bit of solder.
I'm sure others here will have better ideas, but that might be workable.