The user Mich262 from the German Spyderforum has found a lockable fuel cap for the Ryker (https://www.spyderforum.de/showthrea...ll=1#post74366). This fits and can be locked. To order here https://www.carid.com/gates/locking-...mpn-31859.html or https://www.ebay.com/itm/Gates-Fuel-...-/113683971053.