Here is a thought, somewhat related. I dont know if "they" still do it, but right at the entry to the Cathedral there was a bunch of "souvenir" books available when I was there in June of last year. Not the little cheapy ones - more like something you'd by in the Museum store. Not overly large either (although I would still probably mail it out home instead of walking with it to SdC and possibly beyond).....
Anyways, if that is still true - grab one (heck do so anyway!) and when getting your Credential stamped with Sello - ask if they will stamp the book (the inside black left cover page for example). Honestly I see no reason for refusing to to so and hopefully they wont
IMHO, that would make a GREAT gift for either a clergy or an architect friend or acquaintance you may have.
I did grab a book with intention to present that to my Pastors (husband & wife team, and she was instrumental in me "finding" the Camino and obviously embarking on it) but I wish that I had the Sello in it for them