I would ask for it during the interview or ask for a business card. If the interviewer is so evasive they don’t want to give that info to a candidate, probably not a company you’d want to work at.
It’s not a matter of evasiveness. In my personal experience, it’s just how things happen in a lot of public institutions. Private corporations may be different; or it may be different at higher levels of the ‘totem pole’ than I have experience with. I’ve only worked for public organizations and small businesses.