This vinyl case is listed as a 'Children's Luggage and Carrying Case Tote-About' in the Merchandising Supplement from the 1967 Snow White pressbook. Suggested retail price $1.59.
Tote Promotion, 1967 Merchandising Supplement (p.9)
It's marked "Ideal Toy Company" and "Walt Disney Productions." Although the above ad does not refer to the tote as a "lunch box" per se, it probably was used in this way by many. "Measures 8.5" x 6.75" and 4.5" deep.
Case images via sunnyseller2000.
The case appears in the Larry Aikins book, Pictorial Price Guide to Vinyl and Plastic Lunch Boxes (box #175).