Try this link http://www.womacknursery.com/index.html

I have been told that Guardian's release (probably as seeds) is restricted to certain nurseries that then graft upon the seedling rootstocks. I got mine by buying the peach trees from a nursery in Tennessee. The name slips my mind but the nursery is mentioned here on occasion. If not outright patented, I plan to try some root cuttings to get some more rootstock for my own purposes.