hi,
have you found any yet ?
i use the 1/4AAA battery packs from KAN as a replacement.
http://www.kanbattery.com/products.htm#
they are very fine and come in readymade packs with leads
to solder onto.
sorry to say i don’t know were to buy them at the moment.
(i do know a private seller in europe)
replacing the internal batteries is a good idea.
about 25-50% of the original konami packs are starting to leak by now
and are very capable of destroying the PCB.
(i have some pictures on my webpage)
my advice, at least remove the old pack before it’s too late.