Want to mount a big ol' fan to your Printrbot Jr? This is a thing that could do that for you. Not exactly sure that the airflow is all going where it needs to be, but it will make your Printrbot Jr look like a Mazda Miata with 4 ft spoiler. Do it.
Print pieces out and bolt them together with an 80mm long bolt. Adjust to desired angle and tighten. Friction and the holes in the side that catch the nuts may be enough to hold it on to the hot end casing, but if not, try a little double sided tape.