Power Steering control valve part discontinued

I’m rebuilding the power steering control valve on my 72 stingray, the exploded view of the valve shows an o-ring between the Key (plug to sleeve) and valve shaft washer. The rebuild kit doesn’t provide one, GM says it been discontinued, and the valve didn’t have one when I took it apart. I rebuilt the valve because fluid was coming out the ball stud and this o-ring /seal appears to be what prevents this.
Any one know about or has run into this.
The GM part # is 5691199.

Contact Ernie at Willcox@bellsouth.net (Willcox Corvette Department) and he may be able to direct you to a source. Or even send you one. Otherwise, contact a rebuilder and ask them where they get their 'O' rings. Ebay has sellers of rebuilt units.
Good luck. I quit rebuilding stuff and now buy those things already rebuilt. They have warranties. And 'O' rings.

Scott