Lensmate LM X-T20 thumb rest for the Fujifilm X-T20 made out of aluminum fits both the Fujifilm X-T20 and X-T10. It comes in two colors and had silicon on it to grip the camera better. The dimensions are about 63 x 13 x 24 mm and it weights about 8g.
Lensmate LM X-T20: Amazon