The RWS stuff was made in East Germany.
Hornady uses/used Russian cases before coming out with their brass cased version.
The USSR, Poland, Bulgaria, Romania, and East Germany made it during the Warsaw Pact era. Hungary and the Czechs did not because they had to be different.
Ukraine is out since their factory was stripped of machinery a few years ago.
Yugoslavia, Indonesia, Kahzahkistan, and North Korea make it or made it. I think one or more of the other "Stans" have made it or offer it, but I forget which ones.
Any ammunition manufacturer can make this round. The question is demand vs. minimum orders. An importer would have to gamble that they could sell X-millions of rounds to secure an order from a manufacturer, assuming a manufacturer was willing to tool up for making this round.
Outside of the Bulgarian and Polish surplus, I don't think any 5.45 has been imported in the last 7-8 years from any where but Russia and maybe a small amount of "Red Army Standard" from Romania.
Personally, I predict this caliber will fade away as what is in the country now is used up or squirreled away and whatever gets imported from elsewhere is too expensive.