After breaking and losing a bag strap buckle and searching for a 3d design to print and replace it, I realised that a fully parametric replacement strap buckle clip thing would be really handy, so I could …

• retro fit it to fix the one I broke and lost
• add more of these to other bags I own which have annoyingly flappy straps and which didn't previously have such a solution!
• replace strap buckles in place - with no sewing or un-stitching of existing straps required

Parametric design … using Fusion360 FREE to hobby makers) you can change most of the the main dimensions. 

→ Design → Modify → Change Parameters

• Change the width and length of holes, spacing between them, thickness and depth of buckle, how curved the top is, strap cutout / slot size, corner and edge fillets, etc, etc
• The included .stl file and fusion360 file is for a 25mm waist pack strap

Print … 

• simple and quick (took only 6 mins for attached .stl)
• I used 16mm layer for smoother curved top layers
• print flat side down 
• infill will depend on size of buckle you make 
  • 100% was fine for the example stl file and should add strength
• probably best in PETG 
  • ASA, ABS, maybe even TPU and other filaments should print fine depending on your needs

EDIT: 30/09/23 added a couple more  .stl files as examples, 40mm strap width buckles … “thinner” one works fine, the other is simply a bit more robust and chunky. (100% infill petg printed great)

If you like my designs and want to help fuel more shares, then filament donations are gratefully appreciated here on Paypal