Grand Talisman:
* You can craft as many as you want. If you have to ask how to go about doing that, you're not really playing this game as intended, as you would know how by this point.
* The story has offered a few. Consult a walkthrough.
* With the new Master Guide, you can farm for them and, theoretically, find as many as you can. But, you might miss a few birthdays.
With this Master Guide, you can now farm more effectively. Even without an intelligence boost, there is a notably greater mix of silver talismans. You can also stumble onto a gold talisman at the entrance to Estero park, which was Evie-guaranteed(?) to be impossible a few updates back. As for the grand talismans, each time I found one I also had the (2 Golden talisman) intelligence boost, and the grand counts just the same as the gold towards exhausting the boost.
You now find gold talismans much too fast for the current intelligence boost to have much use. I would speculate that a new treatment at Dr. Jessica's is forthcoming- involving anal, of course!- that will give you an effectively perpetual intelligence boost, on a parallel to the Pricia's awareness boost.