Well if I could ever find a T17 pedestal bulb holder as a pattern to make a reproduction out of urethane and see if it is feasible to do and then if so, then later use better materials like acrylic.
Urethane is a good choice to make prototype parts with.
It is easy to use, sets up fast, makes very accurate parts from silicon molds.
Then you can get a good idea of what is involved.
I don't think there would be a big market for the T17 bulb holders, but there might be a special small volume market among fixture restorers, so the per part cost would be on the high side depending on how close to the original you wanted.
The closer to the original, the higher the costs.

For example, a T17 pedestal bulb holder that looked like an original, but you had to solder the wires to the bulb pins and it would not be seen from the outside, would be cheaper than a bulb holder with all the plated contact parts.
This may not be a problem for display uses as it is not like you are replacing the bulbs all the time.
In this case a $20 part X 4 might be better than a $60 part X 4.
But you have to find a pattern part first.