Ah yeah. I've bought some random aluminium BT mouse, it the charge port is on the front therefore the mouse can be used while charging as a USB mouse without an

Ah yeah. I've bought some random aluminium BT mouse, it the charge port is on the front therefore the mouse can be used while charging as a USB mouse without any problem. I also have an old Philips electric shaver. When the battery dies in the middle of a shave (obviously that's always while in use that the battery dies, unless you shave only twice a year), I can plug it in and use it while plugged no problem. So I have a simple solution for OP: choose different brands.