Unfortunately I don't have any link to such a job post, but when I've seen them in the past they've clearly stated what they are about, so keywords like "COBOL"

Unfortunately I don't have any link to such a job post, but when I've seen them in the past they've clearly stated what they are about, so keywords like "COBOL" or "Mainframe" would certainly find them. Sorry I couldn't be any more help.