I have created a minimalistic modular LED holder. The versions I have published are for 5mm LED in two formats: single row of 10 LEDs and a 10x10 LEDs square. The design permits the concatenation of multiple modules and still keeps all LEDs equidistant.
You are more than welcome to approach me if you would like to have different versions of the holder e.g. different LED size, different holder size, etc.

Geeetech i3 Pro B

Doesn't Matter

Doesn't Matter

LH: 0.2; EW(min): 0.315; EW(normal): 0.51

100

It is important noting that the LED separation is dictated by the extrusion width (EW). For instance, the published design has perimeter of 0.315mm (distance between the LED slot and the outer border of the holder). In this case, the separation between two LEDs is 0.315x2=0.63mm. 0.315mm is the perimeter extrusion width I set on my slicer.