Accidents happen and on the rare occasion of a broken clip, you can get one clip replacement fits either left or right shoe light. Specify which color and model - Red and green clips are used for the Night Runner 270 and the larger blue clip is for the Night Trek Xtreme model.
To replace the clip: Turn the light unit on it's side on the edge of a flat surface so that the red clip is on its side. With a small hammer and small punch carefully tap the dowel that holds the clip to the unit down and out. This may take some time and care but it will slide out.
To install new clip, reverse the process. Here is a quick video to show you how its done: https://youtu.be/LRuR16w70Fk