There is a good led conversion for the Solitaire over at Lighthound
Lighthound Pro
It provides a decent spot beam with good side scatter & some focusing ability. The spare bulb in the tail cap can be substituted back in if necessary. Light output is better than stock & closer to white (slight bluish tint on the one I rec'vd). Four hour run time.
Con
The lamp bezel will not screw completely down. This interferes with the o-ring seal some (the one I tried it in fails the blow test some even w/o the upgrade). I'd rate it at least dunkable. Maybe better if the light had a good seal to start with. You might be able to replace the factory o-ring with a thicker one & get a better seal.