Hello all,
Just so everyone knows and there is no confusion. The SL20X and SL20X-LED versions of this light are different. The Terralux conversions built for the SL20X will work for the SL20X-LED as well. The battery packs, however, are different between the two. My LED model has a long thin pack with both pos and neg on one end. The others use a shorter fatter one. The reason I know this is because I just ordered the battery that was suggested above, the 3500MaH one from battery junction. Needless to say, for some of you that know a little more about flashlights than me, it fits, but does not work due to the arrangement of the pos and neg. I did, however, get it to fit and work with a little soldering. Post if you'd like help ordering one and getting it to work. The battery really made my light brighter! My old battery was only putting out 5.2V fully charged. The new one is at 6.3.