Suits a 40mm apple watch.
This is free because it's good luck if it fits.
I dremelled mine to fit inside, then enlarged the STL model, but I won't know if it will fit yours because I haven't done a print test. 
Printed at 80% infill to give the front stability.
Not silicon or flexible material, just standard PLA.
I suggest you play around with it! Blend file is included. Have fun.