This is a cheap replacement for buckles. All the design work was done in OpenSCAD with several parametric values for customization of your buckle application.
Technical
See http://www.appropedia.org/Parametric_quick_release_buckles for full printing instructions.
You should tapper the center shaft to make it self-centering and thus easier to insert.
The bending arms could also use some rounded corners or tapper where they meet the main body, so they don't break early.