My kid broke her croc strap and I didn't want to buy flexible filament and reprint the whole strap. So I made this little jig.     

Print laying flat so that the first layer looks like a rainbow. Use supports inside the channel. 

To use: (See pictures)
Fit the jig onto the shoe, it should snugly surround the rivet. 
Fill the channel with glue. 
Fit the broken strap around the rivet and through the jig channel so that the strap break is near the top of the ‘rainbow.’ 
Use a pin to hold the strap in place until the glue has cured, then remove it.