We did buy Uranium from Russia because it was cheap, but they are far from the only suppliers. Half the world can mine uranium: https://en.wikipedia.org/wiki/List_of_countries_by_uranium_r...

Even Germany had Uranium mines in the Erzgebirge. They just were closed due to environmental concerns and the iron curtain falling, which is also why there are no more "official" reserves. There was no exploration done after 1990, so known exploitable reserves in Germany are low. But that's just because nobody went looking.

Uranium isn't rare and it isn't really expensive. We just need so little of it that there are not a lot of running mines.