Replacement parts for bicycle/moped umbrella holder

So I have this umbrella holder for my bicycle. No, really. Here it is:
http://www.amazon.com/gp/product/B005GNTB4M/ref=wms_ohs_product?ie=UTF8&psc=1

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 al