Regarding lantern batteries, these are not easily find in Sweden anymore, and when found they are usually quite expensive. Four D cells has a bit lower capacity but turns out cheaper in the long run.
The snag though is that if we do not buy them they will be discontinued someday.
You need an adapter for D cells which add to the costs so what you pay for the batteries and how often you use your light determine the payback time, unless you make something up yourself.
I use this one in one of my torches:
https://www.conrad.com/p/mpd-ba4d-s-...-65-mm-1555524