The exchange of a similar valued good

Many peasants may readily trade supplies that are too cheap to be concerned with their gold value. Instead, they may simply trade similar cheap items or menial jobs, so long as it doesn't seem outrageous.

Perhaps the merchant needs a bundle of sticks, for building a fire; or a collection of flower petals for their medicine.

If you're already headed in the direction maybe they'll ask you to send a message since it's not out of your way in exchange.