For brass mouthpieces, Schilke has been doing this for decades (to the extent possible concerning technology at the time). I had a few experimental mouthpieces made by them. Rim curve, depth/shape of initial recess/cup, taper to the bore, and bore depth/diameter all customized. Heck, they even stamped my name on the side as a custom mouthpiece back in the 90s. There is an actual RHarvey trumpet mouthpiece in their records somewhere. If I recall (and this was long ago) I think their code was a 6B8C made for my MFHorn bore (large) back in the day ..
I think I customized it further by adding a pickup to it .. I'll dig it up and post a pic for fun.

For 3d printing; I found it quite interesting that the military could 'sample' say, a tank part and have it created overseas years ago.

It IS fun to see another technology reaching the point where it is accessible to us musicians.
Edit:
Sure enough; found it in the MF Horn case with a BB pickup still epoxy'd in .. hey it works!
If anyone wants a one of a kind custom mouthpiece like this I have 1 left.
Starting price around $120000000000000000000000000000
Hey it's one of a kind!
Soft rim, shallow initial cup, tapered bore to the deep end (on a curve) and large end bore to accommodate air flow for large bore horns ..

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I do not work here, but the benefits are still awesome
Make your sound your own!