These are intended for knives, but there's got to be a way to use them in flashlights. NRC approved, and seems nicer than removing the capsules from glowdiscs.
http://www.tadgear.com/edged%20tools/tad_gear_tritium_thumbstuds.htm
http://www.tadgear.com/edged%20tools/tad_gear_tritium_thumbstuds.htm