No secret, Dan H . located a source for a plexi-glass that is the correct color. It is 1/16" thick and the color is a solid transparent.
I used the dimensions of the original lenses for size. Took a few tries to determine the best way to cut the plexi, but got that figured out.
I tested a new lens and an original lens in a spare instrument cluster and determined that the new lens allowed too much light from the bulb to come through. The other thing , was that the new lens was too shiny to look correct from a drivers prospective when looking at the dash cluster.
So, the new test lens was media blasted on one side.
This gave a good appearance from the drivers prospective, but still did not defuse the light from the bulb enough. Final result was to media blast both sides , that diffuses the light well and gives a good look to the indicator when the bulb is lite. The media blasting also gives the new lens the mat finish of the original lens.
There is also some time invested to hand sand the edges and slightly round the corners of each finished piece.
Simple !
From a practical cost stand point, it doesn't make sense to make a single set.
I had previously looked into doing this from a number of different ways. The use of the product Dan found , results in a quality product that should last without fading.
Loren
