I had the hero's daughter ask him for a gift when he goes on a journey.
I put in a fair so he can buy one and make some allusions to a fairy tale he's not getting into and, more to the point, not getting his daughter into. (Which would benefit him but throw off the rest of the tale.)
So, at this point (and no earlier), does it occur to me that he would also buy something for his wife, the daughter's stepmother. Oddly enough, though I've read a number of stories in which the plot separates the hero and heroine, and a number where it's because he has (for one reason or another) to go on a journey, the number in which he gets her a present even for his return is -- zero.
I shall just have to work out what he could get her. Jewelry and silk dresses are the sort of things wicked stepsisters and vain sisters want. Embroidered works might be more to her taste, but then, she embroiders herself -- perhaps embroidery floss?
I suspect it may have something to do with sewing. It fits the tale. Perhaps a harp or a lute?
Hmmmm. . . he can think about it while he wanders the fair. And notices that no one is selling an apple with a price higher than gold (to slither in another tale).