I saw the original buckle clips a while ago and as I found that the design is really nice I printed a couple of them. However I found that some things could be optimized, so I did it using blender. Below is a list of issues and improvements I made:

• the clip detach itself when pulling hard on it:
  • the side locking is now improved with a kind of "fishing hook" mechanism (the lateral ends of the male are now like arrows that locks even better when pulling the parts apart)
  • reduce the lateral clearance of the male part inside the female part, thus avoiding the male part to make a lateral bias angle with the female part
• the strap slips in the buckle when there is a small angle between the strap and the buckle clip:
  • "compress" the back of the male and the female parts to force the strap to make a higher loop angle
• one have to tune the scale of the parts to make the male part going into the female one
  • adjust the scalings to fit perfectly
  • reduce the female (positive) track height, increase the male (negative) track height

With those improvements the buckle clip are now really strong and fit perfectly my needs.

The scale of the buckle clip I provide will fit 2cm width straps, you can scale it up (or down, but not too much). I scaled it up to 180% to fit a large strap and it still works well with PETG. However the clip is a bit too strong with this large scale so I made a second male version with weaker male "legs". It should work only for large scales (let's say from about 150%), but I did not tested it, please let me know if you test it.

You should only print with materials that allows for bending like ABS/PETG, PLA may not be flexible enough. Enable supports for male and female parts, and don't print too hot (or with fan turned on) to be able to easily remove them from the female part.

If you print one, please post a make or a comment !