Off the shelf dual axis slew drive similar in principle to the one "st1" linked to. Heavy wedge needed, they are not cheap for a dish of this size and weight, start thinking in bags of sand.
or
Fabricator to make custom polar mount from scratch using box section, steel plate and flange mounted bearings
or
Existing polar mount that can be modded by a fabricator to accept the dish
In all instances, the motorisation is going to cost more than the dish on the assumption the dish goes for a monkey or less.