Chargeable wax melt burner.

Does anyone have any idea where I can purchase a USB chargeable Wax Melt burner for the bathroom or even a battery operated one. Every one I have seen are electric plug ins or tea light candle ones. I know we are not supposed to use normal electric plugs in the bathroom for safety reasons but I thought a re-chargeable or battery operated one would be fantastic instead of having to buy those horrible scenty things that stand on a shelf. I have searched everywhere online. I think if someone does come up with this idea they would make a fortune as I never go out without ensuring the electric wax burners are turned off. With a rechargeable one, it would not matter as the charge would run out.