Malagoli
Luiz Malagoli operates Malagoli Elétronica Ltd. in Brazil. In addition to the electric cavaquinhos his company builds, there's also an extensive line of Malagoli pickups, both magnetic and piezo, including this dual-sensor model. I hope it's not too much of a stretch to suggest that you could install this in a mandolin. For more information, visit the Malagoli Web site.