I have a Kryptonite Kryptolok U-Lock for my bicycle.  The lock has two O-Rings that can be positioned so that the lock does not rattle when riding your bike.  I lost one of those O-Rings, so I whipped one up.

I printed in Creality CR-TPU. I used the default TPU settings in Orca Slicer. 

I printed the first one with 100% infill, but it was way too hard.

I printed the version that I am using with 40% infill, and it is still quite hard, but works well.  I would suggest max 40% infill.  If I needed to print this again, I would try 30% infill.

With 40% infill, it used less than 2 grams of filament.

If you are interested, the specifications of this O-Ring are:

• Outer diameter 19.5 mm
• Inner diameter 11.5 mm
• Thickness 6.5 mm
• Fillet outer edges 1mm