I needed a gasket for the Bafang BBSHD motor because the paper one ripped when I was servicing the motor. I made it out of the softest material I had which is TPE. I doubt that TPU would would work unless you used a gasket maker compound in addition to the gasket I made to ensure it sealed well.
In the future I intend to make a mold from my designs so that I can make the gaskets out of better material such as silicone.
I also designed the seals for the wires because getting off the silicone destroyed the original seals.
Print nice and hot to ensure a solid print. I tried putting the flat gasket in the oven at melting temperature on a flat piece of tin foil to melt it into a more solid piece. Wait until it cools completely before pealing it off the tin foil. Not sure if this was necessary but because the print is so flat I thought it would work and it seemed to work well.
The wire seals can be made out of TPU.