I think this may be a long shot but I'm hoping someone here saved what I'm looking for. I'm deleting the ABS on my 94 miata and where the wheel speed sensors used to pass through the fenders there is normally a blank grommet for non ABS cars. I'm looking for 4 of those grommets. Part number should be FB01-56-056, part 'D' in the diagram. Thank you.

 

Try hardware store, or rubber parts store. Even an auto parts store .... It won't have the right part number but what works, works.

 

20.5mm is darn close to 13/16". I'd just grab a set of these from Amazon and call it a day
https://a.co/d/0airlEAn

I've used similar for the large holes in the firewall where the main harness goes through, and it's been great for years.