You can still get hold of Betalights here at;

http://www.penrithsurvival.com/penrith_survival/55/mia/d/betalight/pid/242045

They are expensive but last many years and require no batteries. The light output is minimal though i.e. just enough to read a map etc. I don't know if you can get them in the US as a 'normal' purchase. I think Lofty Wiseman recommends one for a PSK in his SAS Survival Handbook.