Look on the peg hooks at an auto parts store. They usually have a mixed pack of odd ball fasteners like this. You might pay 5 or 6 bucks, but if it has one of these in it, you'll be done with the project.I recently replaced my fuel filter and after reassembly I noticed one of the nylon 10mm retainer nut were stripped in the thread. So I am looking for a replacement but am having no luck even searching the marking on the nut. Any insight and a source to buy would be awesome. Thank you
Take your stripped piece with you for comparison.
Also, occasionally, at some parts stores, they may have a stash behind the counter you can pick thru.
One more idea, put a wrap of tape around the threads, then try running the nut back on. That might give it just enough bite to suffice. (Make sure you wrap it clockwise )