There are a lot of things surrounding Jesus, the Passion in particular, that would have normally been unheard of. Breaking an alabaster jar worth approximately a year’s wages onto someone’s feet would just not have been done at that time and in that economic group. Friends such as Zaccheus, who would have been in the Jewish landed class, would have had the means and desire to provide Our Lord and the Twelve with a kiddush cup made of a noble metal. Certainly the people he hung out with showed Our Lord understood about real vs. ceremonial cleanliness. On that account, I don’t think it is possible to make any kind of guess what sort of material the so-called Grail would have been made of.
Having said that, any vessel that could have been used could also have survived until now. Without divine revelation, though, it would be impossible to identify an object that has no verifiable description or means of provenance in the historical record.
Even if it were found, it would not compare in value to what we do have from that Last Supper, which is the Blessed Sacrament. Some things are beyond priceless.