The Softopper bed cap for pickups is great- seals well, provides lots of dry space, and is collapsible. But I wanted to be able to hang a shirt or lantern inside, either for travel, or when camping inside. These simple clips provide a mounting point for these items. The bars on my topper are 7/8 inch. I assume all the moderns ones are the same size.

Don't hang anything that you wouldn't want to fall, but so far these are holding up. Edges are rounded and set back to avoid damaging the fabric.

Materials: PETG is best. PLA can't take the heat of a summer day necessarily. It gets soft and can bend. Version C, however, has been working just fine with PLA. I'm printing with 15% infill, which provides a little flex.

I provided a few choices.
A: the basic clip. Fits pretty snug, but might slide on the bar. PETG only.
B: a tighter fit. You can see in my photo that sometimes it will crack when being installed. But on my printer and bars, it doesn't slide.
C: this one takes a little more material, but it seems to hold up OK when printed with PLA. PETG works great. It also handles side loading a bit too.

These only take 10 cents of filament, so print a set, and if it's a little too snug, try printing at 102% scaling, or if it's too loose, try 98%. I have installed mine permanently, and the topper still folds up without issue.