I noticed in the Frequent Flyer today that the Tomato Basil Marinara "supplier has been making this sauce the same way since 1934," a clue that easily leads to this company:
They probably make other items, too.
Some of the ice cream (such as the coffee flavor) is made by Double Rainbow:
TJ's sold Double Rainbow ice cream and then switched it to their own label. Both labels were even in the freezer at the same time. Same ingredients, same ice cream.
What other items sold by Trader Joe's are known to be made by a particular company, confirmed by checking ingredients or other solid clues, not just by a hunch or guess?