i guess “best place” is subjective. Personally I’d start with a phone call to Gutsibits, maybe Fowlers if you want to use UK suppliers… then Stein Dinse (as above) and Teo Lamers (TML). But watch for postage and duty from the latter two.
When do the Italians vacation? August or September? this affects supply times.
My friend is going to try and separate the 2 parts of the caliper tomorrow with a hydraulic press so it just depends if he can get them separated without destroying the caliper.
This is why I always have mine apart and greased ASAP even if bike is brand new. Saves so much aggro later. Learned my lesson with a second hand Piaggio X10, was wondering why I can’t turn the front wheel by hand even if jacked up, I’m not that weak surely?