OK,
My Taiwanese partner found a supplier in Taiwan (specialising in radio remote control cars and whatnot) who had the correct connector for the battery called “1mm-2P” that we ordered 5 on 16/7/2021, and delivered to a local 7-11 convenience store today. The total cost was $TWD200 (!) In my experience, its only possible to get that sort of service in Taiwan.
I tried out the connector immediately on receipt, and it fitted correctly, so I proceeded to cut off the old JST1 plug from the battery and solder joined (matching wire color) wires and heatshrink tubing put the battery and correct plug together nicely. The battery is charging as I type this.
So now the Wio LTE device operates without flashing the battery light. I am proceeding to see how well the device now interacts with Windows 10 to have the device driver load as documented. 