Gary,
I've been through this myself. When I was installing the three cylinder reservoirs on my car, I managed to cut one of the o-rings.
Since only one o-ring was provided with each of the three units, I went to the local hardware store and bought the closest matching o-ring I could find. It wasn't as thin as the original, but I figured it would be okay.
After several months of use, I noticed a leak starting to form at the base of the reservoir. I went to a local race shop and the owner had a box full of them. Like Richard H., he graciously offered one to me free of charge.
Several months later, the new reservoir also began to leak, so back to the race shop I went. The owner again handed me a free reservoir.
When the third one began to leak, I'd had enough and called the Tilton tech line to complain about the cracked reservoirs I'd previously had to replace. They sent me a replacement reservoir with a new o-ring at no cost to me. I've had no leaks since installing them. Apparently, the slightly oversized o-ring was the cause of the cracks.
Mike
