I modified keizi666's Tello Tile Mount ( https://www.thingiverse.com/thing:2943670 ) to instead hold just a small platform. You can modify this to mount or carry anything on your Tello, as long as it's not too heavy.
I tried to find a balance between minimal weight and sufficient size and thickness.
There is a normal "m" version which clears the propellers by using a spacer and an "xs" version which is very tiny and thin, but fits under the props. Keep total thickness of your mounted object in mind if you want to use that one.