The nozzles from Mechatronika use a body from cheap soft iron and all they do is to insert a flat syringe needle, they can be bought cheaply.
For the 0201 Nozzles they used 2 syringe needles.0.7mm (od) 0.5mm (id), and inserted another needle there 0.5 (od) 0.3 (id).
For turning something like that I'd recommend to go and talk with a local company, especially a prototype could be done with a conventional mill (we have a few older guys around in town who still do that and their accuracy is pretty much okay)
Doing just a few parts is probably an overkill to outsource to china, the material is cheap and some hobbyists with decent machinery should be able to do that.
Lately I tried to make some cones with a DIY CNC lathe and it also worked out very well, it's not rocket science.
many years ago I outsourced making Mechatronika Nozzles (because they are just not worth their money, they charge like 100$ per Nozzle while the material is a cent article, turning 10 of them cost 90$ back then). Nowadays I'd probably also make them myself if I'd need them.