It'll cost more than US$25 to fix it, since being down here in NZ p&p
will push the battery to more like $40 by the time it arrives. Believe
me- freight can be SUPER COSTLY. Some dirt cheap DIP8 ICs just sent
here from UK had US$20 postage on them...

The request is surely not an isolated one, since it transpires many of
those Yaesu VX-1 Li batteries die after ~3-4 years. As mentioned
earlier I've considered assorted battery hacks/cell repacks for the set
but wondered if this had already been tamed by others. Stan ZL2AJZ