Your search for "Monster 937" revealed the following:
DUCABIKE | Engine Oil Cap
$33.95Machined from solid lightweight alloy with a colored anodized finish.Plug-and-play replacement for the standard plastic oil filler cap.
DUCABIKE | Right Front Wheel Cap Bicolor
$22.13BILLET ALLUMINIUM, ANODIZING SURFACE COLOUREDKIT 1 CAP
DUCABIKE | Right Front Wheel Cap
$16.11BILLET ALLUMINIUM, ANODIZING SURFACE COLOUREDKIT 1 CAP