I know Amontillado was mentioned on the show so I think it likely that if a reference was made to a specific type of sherry in this scene, it was Amontillado. True Amontillado comes from Jerez de la Frontera in the Andalucian region of Spain, but like Champagne, versions of it are produced elsewhere, probably including in California. The writers likely wrote in Amontillado as an allusion to Poe's "The Cask of Amontillado." Jonathan Frid gave a marvelous reading of this story which can be heard on his website.
You can find inexpensive (and good, IMO) Amontillados in the wine section; those produced in Jerez can be a bit pricey but are the best.