I looked at Sparkfun, the site of wonders, and they came back with
The idea is that the IceCube snaps onto a momentary switch with a long
button (which they sell for 50 cents), and you put whatever LED you
want next to it. It should be really straightforward to design small
PCBs that should fit in the space you have. The main drawback is that
they are square, not circular.
Another way to go might be
, as that may have a separate LED that can be customized. There's
several types in DigiKey, but none that can obviously be customized.