I had a hard time seeing what happened around the nozzle of my printer, and I got tired of holding a flashlight, so I made this little fixture. It is designed for the $200-level printers that you can get at various resellers that contain a U-shaped metal bracket on the X axis that is mounted on two linear bearings at the top and one at the bottom. In the top bearings, the lower outer screw hole is not occupied, and that's what the bracket of this fixture is screwed into. For the actual lighting, I soldered some white LEDs onto experimental circuit board and glued/press-fitted it into the slot of the lower part of the fixture. The two parts are assembled using M3x25mm screws. The whole design is parameterized - if necessary, simply adjust the values in the OpenSCAD file and re-render it.