Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:2221139.
After much trial and error, and several revisions I finally got these little guys working great. The clip attaches securely to the (20mm) frame of the Prusa i3 (3DP-11-ATL), and the opposite side securely holds a 10mm LED strip! Once secured the angle of the LEDs is 23.5 degrees, which ended up being just right for almost every print I could throw at it.
To install, first clip it to the inside of the printer frame (facing the bed), on all 3 sides, hold up your LED strip to test for length, and cut to size. Then starting at one end, put the LED stip into one side of the clip, then the other side. It's a snug fit so you might have to use a little force, a fingernail, or plastic pry tool might help (but a screwdriver might damage the strip). Work your way around, one by one, until finished.
Edit: The "LED Clip Final stl" is for mounting the LED strip on the outside of the frame. The "LED Clip Inner Final stl" is for mounting the LED stip on the inside of the frame, this is useful for places like where the control board and power supply mount to the frame (on the 3DP-11-ATL), and the outside clip wouldn't work. These inner clips are designed to be a tight fit, and twist into place, when installing them, take note of the 45 degree angle on the shaft, as the clip will only turn in the direction of the angle. Not the other direction. If you print it out, and give it a try, you'll see what I'm talking about.
Enjoy!