So on the DIY side of things there's printing your own dial with an inkjet printer on a piece of sticky paper.
Here's a good video on that by Mark Lovick, the guy who has those watch repair classes
https://www.youtube.com/watch?v=kt1nmSqS-Ps&pbjreload=10
Here's a good writeup on that same topic
http://www.stefanv.com/watches/making-custom-watch-dials-1.html
I think there are also a couple of threads in the tech section of this forum where people detail their experiments using inkjet printers, but I am not particularly good with RWIs search function so you'll have to find those threads yourself haha
For paying someone else, it seems that helenarou does custom dials though they don't say what techniques they use, and there are these people as well
https://selcotime.com/services/custom-dials/ there are also alibaba vendors. The problem you run into of course, is minimum production requirements, nobody wants to do a one-off.
I personally don't trust the quality of an inkjet printer to last 40+ years against UV damage. It might be interesting to do experiments with e.g. a UV light to see how much damage a watch dial will undergo before it begins to degrade for various methods of manufacturing.
Anyways if you do find more information and ultimately choose a route to go on please do update this thread, I (and I'm sure many others) am interested in this topic and hopefully there are some better answers out there. It seems to me that if you're willing to pay a few hundred bucks and use photoshop/illustrator, you should be able to have your own custom dials, without having to do the work yourself. But yeah, I don't know who it is who'll do it.