It is easy to lose the e-clip for the seat mounting bolt on Harley-davidson motorcycles.  A replacement ends up being expensive due to shipping costs.  I designed a print to clip onto the bolt and retain it to the fender.  This clip is more snug than the stock one to remove play.  Please keep that in mind when installing it, you may need to push down on it to get it to tuck into place.

I used white PLA as a demonstration to make it easy to see, but I would use color matching PETG.  PETG is good in the elements such as sunlight and rain.  PLA will degrade over time in such conditions.