When I visited the UK in the distant 1991, a friend asked me: "Are you all right for money?". I presumed that he was asking if I had enough money to see me through. The expression popped up in my mind the other day, then I tried to google it but no results were available. Neither have I heard it ever since.
My question: Does the expression (still) exist in the English language, or I've simply misheard it?
It does still exist, and you didn't mishear it. If you Google Are you alright for money?, it shows dictionary entries for Are you OK for money?, which has the same meaning.