carbon zinc and zinc chloride are only good in very low drain devices.
and if you can get then cheap or free.
dollar tree cheapies do fine in low drain led lights.
and that class of lights is mostly disposable anyway.
in an emergency those may be all you can get.
as for $to wh i have never...
nicd and nimh are very unlikely to leak unless abused or poor quality.
i have nimh d cells from 98 that are still good.
but those are panasonic oem for honda.
most nicd or nimh leaks are minor and do little damage.
as for safety i wouldnt worry.
its a major mfr not a whateverfire junker.
the very few failures i have seen were bad solder joints and dirty contacts.
every one of these older chargers i opened had thermal fuse in the transformer or if smps based a fuse resistor in sleeving along with a line...
i have opened laptop packs 12 years old with cells at 2.5v.
and they were like new performers.
the big problem if this is the real vapcell you are dealing with is lack of care.
if it were me i would make a note on the transaction and go pull some stock to test.
yes i imagine most calls they get...