Provisioning writs you can buy the finished goods and turn them in. Has to be green, not white, so player-made purchased from a guild store. I've been doing this for Ginger Wheat Beer since I can't find the recipe anywhere.
Babeester Gor is the Axe Goddess, the Implacable Anger, the Avenging Daughter and the Earth Guardian.
Vriddi gra-Yildnarz, Dragonknight and Smith
Myrvanwe, Sorcerer and Enchanter
Tsajirra, Nightblade and Clothier
Vilvyni Indarys, Dragonknight and Woodworker
Arielle Alouette, Templar and Provisioner
Fishes in Troubled Waters, Nightblade and Alchemist
Shanika Some Long Title I'd Change If I Could, Templar and Aspirant Jeweller
Pippi Longhorn, Nightblade, Ne'er-do-well, and "Tribute" character
EU PC.
For provisioning and alchemy you can use goods produced by someone else. If you want to find crafted potions in guild stores you'd need an add-on (I use one called Crafted Potions).
I believe all of the other crafts require you to make the goods yourself, probably because those identify the maker on the items.