Maglite Switch Bump Tool

Here's the problem with Maglites: they last a lifetime - contrary to the batteries you put into them.

As i recently discovered, cheapo D-cell batteries definitely have a lifetime much shorter than Maglites. Not 25 years (which is roughly how long i have my Maglite already), and probably also not 10 years (which is how long ago i last used it).
I'm unsure about their actual lifetime, but i guess if i had replaced the batteries in my Maglite 6D those 10 years ago, i wouldn't have had the issue i'm facing now: at least 3, but probably 5 of the D-cells have expanded and leaked, causing some serious corrosion inside the tube, so now they've glued themselves to the inner wall and are totally stuck.
I was able to tap the first battery with a woodscrew (and with the help of citric acid to dissolve some of the corrosion, then some WD40 for good measure) and pull it out - and then i was stuck with (probably) 5 more that i couldn't even get to, as then next battery was already too deep ins