This umbrella lost it’s handle.  It unscrews so if you aren’t careful, it can easily be lost on a bus.  An identical replacement was purchased, and the handle for that one also unscrewed.  We took some measurements and quickly designed a replacement part in Autodesk Fusion 360.  Loaded it into Cura and printed it out on our  Forget-me-not 3D printer.  1.5 hours later, we had a perfectly fitting new handle, in blue to match the opening button on the inside.  We then added a dab of glue to stop the new handle falling off (on both umbrellas), and now we have two perfectly working umbrellas.