Thanks Aurora and iDevice for your further comments.
@Aurora: It is clear now that I significantly overpaid for the 3D print. At the time, I really did not understand why there is a "setup fee", since there is not even a need to convert from the STL file or anything... Now I realize many people do not charge such a fee. In the short term, I will probably use LuneValley3D, until I find an alternative.
You are right, I already have the 50mm FL lens, so I only plan to get the 75mm and 100mm. I will take your advice and simply get two more of georges80 lens holder made --- it will be the cheapest and simplest solution. I have already ordered the lenses.
@iDevice: My experience is very similar to yours --- I had got the 50mm FL lens, but found occasions that it is too close (sometimes due to obstructions on the circuit, or a housing of the circuit board, prevent getting the camera close), so I am getting the longer focal lengths to accommodate these uses.
Also, it's time to mount the E4 on a tripod, so I will try georges80 e4_holder_v2. At the moment I am thinking to have a 3/8"-16 to 1/4"-20 adapter (see pic attached) inserted in the holder. Did anyone do it differently? I wonder if anyone used a 1/4"-20 thread directly into the holder? Will appreciate to hear peoples experiences!
Cheers!