So I have this umbrella holder for my bicycle. No, really. Here it is:
It's a great design and a great price, except for two problems. First, tightening it to the handlebar tight enough to hold the weight of an umbrella is tricky; my first try, I made the bracket snap in half. Second, and more damningly, the clip that holds the umbrella handle itself has a weak spot and is very easy to snap; I've broken two already.
So I set out to make replacements. The bracket replacement wasn't too hard. I made it more solid than the original to help make up for the fact that 3D-printed ABS is not as strong as injection molding. I haven't put it through the ringer yet, but it feels as solid as the original or more so. And you can always print more.
But the bracket clip is much trickier. It has all kinds of angles that are tricky to print without supports without them ending up not as smooth or solid as I would like (and printing with supports makes weakness of a different sort when you cut and file them off), and a very narrow spot at one end, where the whole thing pivots, that feels impossible to make strong enough in the limited space available. There is also a hole down the middle of it at an angle that I could never get right, and in the end, I just printed it solid, then put the hole in with a drill and smoothed with a Dremel. That means no hex-head countersink, but it's not really necessary.
I have been able to install this clip, but I'm not sure how well it will hold up to actual use. My fear is it will break more easily than the original (though probably in a different place). So I am uploading this both in case it might be of use to someone else (though really, what are the odds someone else has the same mount I do?) and in case anyone has ideas for a way to replace that clip that won't suffer these problems. For that reason I also included Google SketchUp 8 files.