As was said, you could assemble one yourself if you find a panel mount variac without a case. I think Powerstat was another brand name.
https://www.antiqueradio.org/Variacs.htm
If you buy a modern unit pre-assembled unit I don't think you should have many problems as long as the current is enough. Be aware that Chinese units might not be up to its rating, a 5 amp should give you some extra cushion.
There actually are some that also combine a variac and an isolation transformer. Check carefully.