Here i have constructed a backpack holder for a "Garmin Oregon 450" (and similar)outdoor navigator.
-0,25mm layer thickness
-STEP file complete (with all parts)
-STL files (part1, part2, part3, part4,(part5 add for smaller belts))
For better holding and against twisting:
Put a sealing ring (~âŒ€16mm x âŒ€22mm x âŒ€1mm) between part1 and part2