This
type of holder (if not the exact model) is very commonly used on commercial vehicles and special purposes vehicles such as ambulances. Anyone who does not need to match exact mounting holes may want to consider industrial supply sources for a variety of choices.
The existing holder on my
Boler is the T-style (e.g.
item 46919 in Coast catalog). The type Tom found (e.g. item
46826) would be an advantage over the T-type because it engages automatically (mine has to be folded out and hooked in); however, to hold the curved door far enough away from the belly seam to avoid damage the arm of the holder needs to be long, and since it doesn't fold I wouldn't want one that long sticking out of my trailer. I think they're a better fit for flat door/wall configurations (e.g. a
Fiber Stream?).