After hunting for a perfect glass clip and trying a lot of them, I decided to design my own. The objective was to allow easily cut pieces of glass to be used and still keep as much of the bed available for prints. These clips are very specifically designed to fit a Printrbot LC with a UBIS hot end, the wooden bed and 6 inch bed heater. The clearances may not work with other configurations. The clips will securely hold a piece of 6" x 5.5" single strength glass (1/8 inch) perfectly and allow you to print on most of that space (due to the angled edges of the clips. It attaches with normal screws which end up sunken in the clip so they don't get in the way of the print head.
Print with high infill (you want these strong) and in ABS (you don't want them to melt). This is designed to print fine without support. Note the clips print upside down and you'll need four in total for the bed.