[Wids]

A Boot of Tumbling is a Boot of Tumbling, no matter where you find it. If a quest giver says "Bring back two Scrolls of Magic Missile; you should be able to find those items in the Main Crypt of Bezantur's City Tombs," you're just getting advice on where you might find a Scroll of Magic Missile or two. If you find one Scroll of Magic Missile in the City Tombs and loot the other on the plains between Murbant and the Keep of Sorrows, the quest giver doesn't care; he'll still take them both. Same with buying one of the items and/or crafting it yourself.

Tristella had a quest like that, as I recall. She had to bring a townie two Rings of Sorcery I. She found one ring in Bezantur's lower sewers (where the townie advised her to go) and she looted the other one off some random street thug. She finished the quest. ;)