The VA signifies Viaccess and the OTV Open-TV. But both of those terms are applicable to several receivers. For example, there are models called VA-5200 and VA-FOX, and the 5600 range has built-in OTV capability.
But the only mention I found of something actually called "Humax VA OTV" was at a Danish website. Seems this model may be specially produced in Scandanavia for the Viasat home market.
Try searching a few Scandanavian satellite shops/sites.