All you need is 2 8mm 10" rods and a longer GT2 belt, both of which you can get off eBay for less than $20 total.
This idea inspired by nucgloworm's model. This can NOT be printed on the Printrbot Play since the width of the part has to exceed the printable width of the printer. I originally wanted to use nucgloworm's design, but I didn't like how sharp it was and how it was multiple pieces (which does make it possible to print on the play but also less sturdy and requires extra screws.) Mine print as single pieces but does require a printer with a larger build volume.
The front piece is a bit tighter on the rods so it should hold them in place. If one is a little loose, use some teflon tape around the end to tighten it up. The rods do stick out of the back a bit but it doesn't cause any problems, just make sure to keep it further away from a wall.
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