[ She knew that her hunch about liking Annabeth at the D&D table had been correct. While the thought of improvement might stem from slightly different sources, it's clear that they both just want a good experience. And if it did turn out that the stamps were the same, what was the harm in making their own?

...On second thought, maybe the two of them combining forces is a bad idea. Alas. ]

I like the way you think.

[ It seems that they aren't the only ones participating in the hunt. Every other person they pass seems to have a booklet in their hands too. And while that isn't interesting in and of itself, what Hilda does notice is that none of them seem to have the vaguely tired look of those that have been kept up by visions and nightmares. It's a good thing of course. But she can't help but wonder if Annabeth had been inflicted with the visions too. ]

So according to this it should be in a store front that sells oddities and the like. But there's a couple of those in this area.