USA: Wes Wong of Rare Fish is the only source of Wels in the US that I know of and dealt with. There have been a few others here and there but he is the main one. He sells both albinos and normal ones for $200-$300 US. Even that happens only a few times a year or less.
We all tend to think he sells the true Silurus glanis and not some other similar-looking (but smaller) Silurus species like S. asotus or S. biwaensis, etc. But no one appears to have grown theirs to beyond 5'-6' to be 100% sure.
AFAIK, there is some work occurring in the Dept of Wildlife to possibly ban the Wels but it's been going on for a decade at least and perhaps they decided Wels is not a threat. But who really knows?