Thanks very much for taking the time to reply.
Your advice about asking a repair shop to change the battery is sound and sensible.
I'd obviously thought of that myself, the fly in the ointment is non availability of Samsung batteries.
I don't know of a single place in Tokyo that stocks them. The retail outlets are totally dominated by domestic products, even finding a shop that sells Samsung products is a major challenge.
I know that sounds incredible given Tokyo's reputation as a technology leader.
If you know where I could buy a replacement battery in the US, I'd certainly appeciate it.
At the moment I'm using the tablet plugged into the mains, which curtails mobility but is better than nothing.
Once again, thank you for your kind advice