This light bar for Prusa i3 holds three Piranha 24 LED boards (MPJA.com p/n 32035). It works well with a pair of brackets designed by @wschadow (https://www.thingiverse.com/thing:2055511).
Preferably open the 3MF file with PrusaSlicer. If you use the STL file, be sure to rotate/move it so the entire part fits on the build plate.
Install a 5mm micro toggle switch on either side and wire as shown in the photos. Power required is 12 volts 1 amp.
The LED boards are held in place by friction or with double-sided tape if you prefer.
Project cost < USD $20.