This is a customized version of a lens cap holder that adds fillets to the buckle so that it is a bit stronger. I had some layer adhesion problems originally and I figure some fillets would help. The original design was great and I wanted to keep using it.
I also added the possibility of having a second smaller lens holder on the inside. That way if you have two lenses you don't have to carry around two lens holder on your strap or switch them out.
Depending on each individual lens there has to be at least around a 5 mm difference in the diameters in order for the small lens to fit.
It is also helpful to make the lens diameters as small as possible so that they fit tight and you can get two lenses to work.
For example: on my Nikon I have 72 and 67 mm lenses. The best diameter for the two are 71.5 and 64.5 mm. It's worth pulling out some calipers to get a better idea of the actual diameter of the cap.
Sunlu Wood PLA
TIP: When messing around with the settings in OpenSCAD using lower numbers (~20-50) for the variable "circle_sides" will help it render much faster! However once you have the settings you want, before you export make sure you make circle_sides much larger (>150) and then render, otherwise the fillets will print poorly.
A good amount of top and bottom layers along with some extra walls help make the print stronger. The .scad file I uploaded has the buckle beefed up a bit from the original.
The variables added for the fillets are just 3 radii.
There are also a few new variables for the second lens cap holder.
I printed in PLA, I suppose PETG or ABS would be stronger.