I could not find an acceptable 3D printable rivet, fastener for my Crocs' strap so I decided to make my own. 

Printed in PETG with 0.10mm layer height, no support. Please enable sequential printing at Print settings - Output options - Complete individual objects if you plan to print more than one at the same time. You need a pair to make it work ;-). 

A pair of these fasteners is printed in under 15 minutes.

Attached STL model parameters:

• Total height: 10mm
• Pin height: 8.8mm 
• Pin diameter: 5.5mm 
• Base diameter: 14mm 

These parameters and a few others can be easily adjusted in the source OpenSCAD file.  

I hope you'll find it useful!