As far I know. Ilford and Fuji are the easiest to find. Good kodak stuff is hard to find. I've looked at Casanova's foto page, and they only list TriX in 35mm, about 4.5€ per roll. That's for Barcelona.
There's also Arpi, but I don't know anything about them. Their site has been down for months, but I suppose that they are still in business.
There's a store, near the canaletas fountain. You will see it easily. Full of kodak stuff. I never been into there, but from outside I could see lots of yellow boxes. Don't know about the stuff, it must be all consumer. "Digital solutions", it says there. So I doubt very much if they have TriX, specially in 120.
I don't know about other cities; Madrid, Valencia, and others. In Madrid you should be possible to find anyone who sells TX in 120 rolls; but don't know.