Fully understand your concern, but that is very unusual case where some USB drive not working with our device.
If you buy a regular USB stick like Sandisk Ultra Fit; Sandisk Cruzer Fit; Transcend JetFlash those should work with no problem. There’s no advantage to use USB 3.0 drive because the LP-16 has USB 2.0 interface so you can even use USB 2.0 drives as well. The speed of the USB 2.0 drive more than enough for playback purpose.
But if you decide to go with USB 3.0 standard (because of the faster exporting speed from uTool) go with the Sandisk Ultra Fit we have a pretty good experiences with this drives.
I am also sure your current USB drives are not broken, only the partition deleted or improper currently. That is the reason why the windows cannot mount the drive. If you install on your PC some partition managing app you will able to repair the partition.
We are sorry for the inconveniences