Hi Cave Monster,
Thanks a lot for your post. After a quite intensive search I am going to get the old style 4 hr. plug in pack, NiMH, and a focusable 10W head, plus one more battery pack for multiple dives. As the new style of fully sealed canisters has not flooded the market yet, I assume it will be easier to exchange or repair the older style battery pack. On the top of it, there were some issues with lithium packs. Not only do they lose a large percentage of their capacity every year (based on an article) but also some airlines have strict limitations on sizes. I just hope I can still get the old style.
Lots of safe diving
Zdenek