You can get a replacement O-ring at auto zone or advance auto. I just used a gasket sealer when I did mine.

 

I just used a gasket sealer when I did mine.

x2^^^ I think I may have used gray right stuff, with the old o-ring.

 

I took it by the local parts store and got a generic o-ring. I think it's a little fatter than factory but it torqued up and I'm not leaking. I ran a pressure test before putting it all back together this time and it looks good!!

Took it for a test drive and had to immediately cancel that because the power steering is out. I'll start a new thread for that.