(GARAGE)P designed these fuel cap holders as a way to thank the community for supporting their efforts. They freely distributed the print file for people who wanted to 3D print one for themselves and graciously allowed us to use the file to provide these for people without 3D print capability.
This holder slides into the fuel door and uses an existing stud to hold it in place. The cap snaps into place to hold it out of the while while refueling.
Basic versions are printed in black PLA. A PETG upgrade is available in black only (PETG is stronger and more resistant to chemicals than PLA, but is probably overkill in this application), and a price reduction is available if you really don't care what color your holder is (we're using up some old, oddly colored filament and are happy to reward people who reach into the mystery grab bag).
If you have a 3D printer, the .stl file is available for download here.