We gave it one more try on the way back and had more luck. The market was starting to wrap up but we managed to find a cheese vendor.
He didn't have 36-month-old Parmigiana Reggiono, but he claimed his 28-month-old was better - not too strong.
We gave him full marks for honesty and bought some. He then offered us a taste of Pecorino infused with red wine, followed by one infused with Tartufo (truffles). We bought a good-sized chunk of the latter for €6.75, quite a bargain.
A lovely way to say Arrivederci on our final stop in Italy this trip.