TLDR: Each Master has one item that with give you 5 points towards your bond with them. Below is a list of said items and the place you can find them to purchase.

Blanka Knockoff Blankachan Doll Bathers Beach
Cammy Jellied Eel Bathers Beach
ChunLi Canned Herring Old Nayshall, Shopkeeper Dora
Dee Jay Lukewarm Beer Ranger's Hut
Dhalsim Instant Curry (Ultra Mild) Old Nayshall, Shopkeeper Tsanpa
E. Honda Rubber Duckies Colosseo
Guile Natto Genbu Temple
Jamie Bao Bao Bro Sticker Bathers Beach
Juri Wrench Dhalsimer Temple
JP Antique Playing Cards Bathers Beach
Ken Cookbook Thunderfoot Settlement
Kimberly The Answer Lies in the Heart of Love Bathers Beach
Lily Celery Chips Bathers Beach
Luke Red Elevator 8 Bathers Beach
Manon Beaujolais Bathers Beach
Marisa Cold Tomato Soup Fete Foraine
Ryu Instant Soba Metro City, Shopkeeper Udon, Urban Park
Zangief Wooden Bear Barmaley Steelworks