RoadShowers have been produced with radiator, hexagonal fill caps and currently a round fill cap. The caps are not interchangeable. If you need to replace the fill cap you must do so with the style that came on your RoadShower.
We do not have the radiator style caps but they can be found here and here
Below is information on the other styles
Hexagonal Fill Cap PN 8881260 requires wrench PN 8881261
Round Fill Cap PN 8881263
If you have further questions please contact us here, or by phone at 888-925-4621 during business hours.