I had more than one Tekna dive light in the eighties. They were single cell and twistie head. Not sure what the cell was, I can't find the lights. I do know the cells were expensive, like seven bucks a piece, and were about the size and shape of a CR123a.
They were great lights, much brigher than a MiniMag and easier on the pocket. I had one black and one yellow. In the 90's they both stopped working, but I put the head of one on the body of another and got some more years out of them.
I still have the lights, just not sure where. They will turn up one day, and I'll see what kind of cells they take. Then, if that cell isn't around the house, it will be obtained so the light may shine once again.