Woody, I've tried sending this three times in reply to your message. Let me try this different way:

Hey, Woody, I just went through my photos of the master cylinder swap and do not have a photo of that O-ring. There are two of them, BTW: One on each end of the hydraulic line between the slave and master cylinders. The shape is so odd that, unless things have changed, you'll need to buy a new hydraulic line and it comes with both O-rings. There's no aftermarket for it. Anyway, here's a video that shows the seal. Watch through the part where he shows how to fix a leaking seal ...