Hello.
Is there a way to get/buy original (like initially released, unpatched, unmodded etc.) Fallout classic games that is F1, F2, F BOS (for e.g. F2 1998 by Interplay) ?

Sometimes you can find these games on auction portals. Check ebay for example, but be prepare that it's not going to be cheap. If you're asking for new copies however, I'm afraid it's not possible.