Unfortunately, the Surface Duo lacks Qi Wireless Charging, meaning users are forced to charge the device at least once per day via the USB-C port.
Fortunately, it is perfectly possible to add Qi wireless charging as an aftermarket accessory to your smartphone, with redditor Maahir Madhok doing just that.
This is possible with the use of a Wireless Charging Receiver coil, which is readily available on Amazon.
The coils, which are very thin, plug into the USB-C port, often support up to 15W fast charging and can often be concealed under cases.
They plug into your USB-C port and attach via adhesive to your smartphone, making it a somewhat permanent install, but given the ubiquity of wireless charging these days for many users, this is not a problem, and I can imagine it could be concealed quite well under the popular DBrand skins being used by the Surface Duo community.
Check out some solutions for $10-$20 at Amazon here.