TPU!
You want TPU! You want the mount to be rubber so it can absorb the road/engine vibrations. PETG will simply transfer the vibrations, thusly making the entire point of the print moot.
If you're having difficulties with printing TPU, make sure to dry it for at least 12-hours immediately before printing at ~50c. I have a repurposed food dehydrator that I can dry up to five rolls at a time:
Plus, it packs down pretty well. I added the hygrometer from another remix I saw (I don't remember right now) but that can be purchased cheap from Amazon.
Link to the wall STL is here: https://www.printables.com/model/609825-elite-gormet-dehydrator-extender
Also, if you opt for the Amazon-branded TPU filament, here's a link to optimized g-code that can be used on a Prusa (maybe even other 3D printers???) that will give you the best results with that particular brand:
https://www.printables.com/model/64123-heavily-tuned-amazon-basics-tpu-print-settings-wit
Mike