Tap Spline Drive

This is a bit of a niche thing but my bathroom taps have started to come apart on me. I have 5 mixer taps like this - so 10 spigots in total. They have a little plastic insert that splines into the handle and has a "D" shaped internal hole that locates on the spindle. Once these bits break the handle comes loose and you struggle to turn on the taps. Needless to say I couldn't find the bits for sale on line and HD had nothing like it. I therefore was forced to model in Inventor and after abo