I've been looking for a easy-to-print, low-volume, low-profile snap buckle that would work scaled up to 4"... spope's swivel buckles don't scale, but the basic design kick-started my brain enough that I threw together this simplified parametric design which should do the trick (update: yup).
Update Dec 8/15: adjusted the post geometry for easier/stronger printing (tapers work better if they start a few layer off the build platform), tweaked the tooth design.
Update Dec 11/15: made customizable, minor tuning, cleaned up magic numbers
Tested okay with PLA and PETG. PETG could maybe be tighter.