I have a Fenix sports watch.  The band restraints broke and the band was flopping around.  I designed this replacement and printed it in Yogi TPU.  It has been working very well for me.  The original design has a cap that one can glue on to fully secure the band but I found it to be unessesary.  There are also indexing holes that could be used to secure the restraint for more security.  This restraint is very confortable.  A parametric Fusion 360 design file (f3d) is included for remixes and adjustments.