...All four of you.
Sinmore has an abhorrently nonexistent Order of Hermes Lore, but I imagine when she hits up Great William for aid, he would share his knowledge with you.
The nearest giant-blooded mage to you is Collem Ex Miscellanea, of Duos Flumen. (Former PC from the original, similar-ideas-but-very-different-execution tabletop version of this saga.) He's Scottish, focused on Creo, Auram and Corpus; he may already have a lab text you could learn from. "He's an interesting man, really... he's a known skinchanger, who takes the form of a giant black dog."
There is Fiona Ex Miscellanea, who lives in Normandy. (Peregrine_Bjornaer's character from Bibracte ) William doesn't know much about her, "...except that she always smells like freshly-turned earth, and all the lovely things that grow in spring." He blushes a little, and even Sinmore with her zero social skills figures out that he has a little bit of a crush
Finally, Iohannes of Tytalus lives in the Alps. He is a Vim specialist who favours Intellego and Perdo (know your enemy, then CRUSH IT). He is the Alps' Chief Hoplite, and is surprisingly erudite and well-spoken despite his brutish appearance. Iohannes won a great deal of acclaim (...infamy?) as he's developed a spell that destroys the Gift, which he used notoriously during a Wizard's March back in the '50's. (...the 1150's, that is.) A few Bonisagi thought that if they learned his spell to destroy the Gift, they could use that knowledge to help figure out a way to create the Gift, but that line of research is still completely fruitless, to Will's knowledge.
Great William regrets that he is too busy to assist Sinmore personally (he's the Tribunal recordkeeper and scribe) but he hopes that the information he's provided can help her follow up with her colleagues.