Actually it an old seimans panel
It is on the dead front. No I haven't tried supply house yet and I sure hope I don't have to sell them a new panel. It would be a tough one in block and in conduit.
I-T-E Circuit Breaker Company, Walker Div. is the make, they were a pre-CTL design panel, without notched bus stabs, 1960's timeframe so will be a longshot to find a part. As said above, Eaton retrofit panel may be the best bet.