Yeah, I know is obsolete and old and everything you all might say... But I just needed... This stuff happens... xD any clues?
Rational bought Verdix in '94. IBM bought Rational in '03.
So at this point my suggestion would be to go IBM's Ada webpage and follow their contact information to see if there is any way they could sell you an old VADS system.
If you totally fail at that, I believe Ada Core can be contracted to port the code to their modern compiler. A thourough tested port would probably not be cheap. But then again, I remember those VADS systems going for more than $10,000...