I haven't tried this personally, but these ppl appear to be able to print anything on the keys:

https://www.wasdkeyboards.com/

Some random examples:

http://www.wasdkeyboards.com/index.php/products/make/wasd-87...

http://www.wasdkeyboards.com/index.php/products/make/104-key...

Can confirm! I'm typing on a WASD keyboard right now that has a custom-printed layout that I designed myself (reflecting some assorted remappings that I'd been doing in software anyway—until I got this it had been almost two decades since my keycaps reflected the actual key layout I was using). You download either a template or a complete graphic, edit it, and reupload it with your order. Super easy, and after accounting for the fact that the keys are mechanical, not even that expensive. (Way more expensive than a commodity keyboard, though.)

Not the keycap thing, but I can give a +1 to the WASD company. Just bought a CODE model and very happy with their customer attention.

You might find out this world overlaps with gamers and novelty mechanical keyboard people. Check out a search like "mechanical keycaps custom artwork", eg here's one - http://www.maxkeyboard.com/custom-art-icon-or-text-cherry-mx...

Maybe give these guys a ring and see if they can recommend who they work with for non-Latin caps: https://mechanicalkeyboards.com

And also hang out on https://www.reddit.com/r/keyboards and /mechanicalkeyboards.

The mechanicalkeyboards subreddit is very active, and full of both artisans and information.