First and foremost, use a NEMA 6-50 or 14-50 outlet - never a 10-50 outlet, which has neutral and does not have ground. (super bad). For some reason, welder enthusiasts have "adopted" the NEMA 10-30 and 10-50 as their "private socket/plugs". This is crazy, don't buy into that nonsense. The NEMA 6 series is designed for welders with no neutral.
For Commander breakers, talk to an Eaton dealer. They make a selection of breakers for Commander that are readily available. If you just can't get breakers for it, it's time for a new panel.
If your state has adopted NEC 2020, then any socket will require GFCI protection as of right now. And as of January 1 2023, even hardwired 240V loads will require GFCI protection. If you can avoid a socket, you will sidestep the need for a GFCI, as long as your permit is pulled before January 1 2023.
However, electric vehicle supply equipment (EVSE) that is hardwired will never require GFCI protection regardless of that deadline. Because it is a GFCI (among its other tricks), and you don't need to put a GFCI on a GFCI.