Summary

This clip will clamp an inexpensive USB LED light source to the base of a Printrbot+ (and likely LC as well).

Instructions

Purchase USB-powered LED lights. The model I bought is listed at Amazon as "Energy Saving USB LED Laptop Notebook Light" and sells for $2 with free shipping. I bought 4.

Optional: purchase molex to dual-usb cable. I bought two from coolerguys.com, they're listed as "4 pin Molex to Dual USB 5V Power Connecter". With this cable, the USB LED lights can draw power from the Printrbot power supply.

Printing:
Bring the file 'light holder5.stl' into your favorite slicing app, output gcode, print. I went with .1mm layers and 100% infill. Though I carefully measured the LED shaft and the wall of the Printrbot+ base when designing the clip in sketchup and all should be well, I found that I had to scale the clip in slic3r to 102% in order for everything to fit together, and it's a tight fit. Scaling to 102.5% might make installation easier, but the clips are held in place by friction so at some point scaling them up will become counterproductive.

Assembly:
Snap the round end of the clip over the thin part of the LED light cable and slide the thicker, inflexible portion of the base of the LED light into the clip. Then attach the other side of the clip onto the Printrbot+ base. See attached images for details.

LED light holder for Printrbot+ and LC