Ron my guess is that is going to be pretty hard to find. Anyone who has an original thats still in one piece or 2-3 for that matter owns a 150L that has had lots of love and will never give the part away or sell it.
The real truth however is the originals were made of plastic of the day back in 1972-73 ish and after this many years has turned to small bits or dust. The PMA replacements form Vantage (and others) are made from a superior plastic that will last a little longer.