There are at least two of the guys on vintage Elna group that now and then has made up a small batch of metal pulleys for the Supermatic. They are hand made, on manually operated lathe machines (electrically driven though). There is nothing like the 3D printers we might have in the future, the ones I have seen make stuff out of plastic sticks, much the same as a glue-gun, the result can be impressive from a technical point of view, but still, nothing like the chisseled out replacement parts we are used to. So far "3D printing" has been just a fancy term floating about with out any ground. The plastic use for gears has to be solid and durable, the glue-gun like plastic on some of the exhibiton 3D printers is not this quality.
I'm sure some of the Touch and Sews can be worth it, for medium to light work maybe? On a Singer 66 you run anyting through it with out thinking much. I have to add, I don't know much about the durability of the later T&S models. I regard my Elna Supermatic and my Bernina 730 as tough, every day machines. If something is too hard for them, the needle stops in the fabric, nothing more dramatic. Both have a few plastic gears.