Had to up size the original model to 135% (X&Y) and 200% (Z) as it was especially undersized as @EddieRich noted in his description. Making the Z wider makes it more comfortable and less likely to cause injury.

Use at your own risk.

Printed flat without supports.

Each color is a different brand and hardness of TPU. They all printed out fine. You could probably use any filament (PLA. PETG, etc) you like but TPU likely offers the most comfort. Adjust pliability by increasing or decreasing the walls and or infill. Just experiment with your settings as it only takes a few minutes to print one of these out.

The elastic bands are just silicone o-rings. The tightness of the band can be varied by the size of the o-ring. Here's a link to the actual product page.

Silicone O-rings: https://www.amazon.com/dp/B0BX9RV7HX?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

Use at your own risk.