Exactly where was the leak on the bike? Front, back, left side, right side....can you narrow it down?
There is an o-ring seal on the water pump shaft that is prone to leakage and/or failure. I thought I had a valve cover gasket leak, but it was coming out a weep hole on the upper right side which turned out to be this O-ring & shaft. I bought a valve cover gasket and O-ring for the replacement, as it was leaking a fair amount (not a fountain by any means).
But first, I swapped the oil from synthetic back to a standard grade and the leak dried up and stopped. Probably not same situation you have (especially since you said "Head Gasket" which is much lower on engine), but thought it might be helpful info to know.....as you travel along. Just in case you encounter that issue, as well.
p.s. my valve cover bolts were loose when I received my bike.....didn't realize it at the time. Or, at least, they vibrated loose over 10,000 miles of riding. I was seeing some oil leak from the valve cover until I tightened those bolts down firmly. Yours should be fine, if someone just replaced a head gasket.