I printed https://www.thingiverse.com/thing:1672155 because I needed a shell holder. My dad really liked it and asked me to make him one. I decided to remix the design for my dad as a Father's Day gift. The changes I made include:

• Slightly taller belt loop
• Wider sides to more easily grab the shotgun shell box
• Different pattern

Note: The narrow beams in the design are pretty fragile to lateral stress, I'd recommend a material with strong layer adhesion.