If there's no ID on the panel it's a slim chance you'll find the original suppliers. There's so many sheet metal workshops manufacturing sheet metal DB's and MCC enclosures, I've dealt with at least 2 dozen different local suppliers in the past, possibly more in fact.
Looking at the design you could try Elsteel who are in JHB or maybe Joffe who are in Epping CT....but it's a long shot like I say, I'd usually just measure it and get a new panel made to order by any decent fabrication shop. Maybe try AdrianH, he has a laser cutter.
I am special and so is Vanash.
What i normally do is order a new DB and quote for the install no use in fixing something that you can't get parts for. Or you can have it made but that is also going to cost money "not as much as a new DB" and it will work, it is just why bother? Eventually you end up with "custom this and custom that" and a lot of custom parts will complicate your life to the point where the work will slow down. Consider "time" and "cost" and if it is worth doing the custom fix and or replacement
DISCLAIMER - The above does not constitute to legal advice or formal advice in any manner or form