Find a wiring diagram for a Limited model that would come with that option, and from that locate the memory seat module. You would have to get the module, and the seat motors from a memory seat. Those are the most unique parts that you must have. The switch is not hard to buy or deal with, but the rest of the wiring is ideally taken from an existing vehicle with the option.
The number or wires should be similar, though models that also had memory mirrors would also have a bunch for those also. If the mirrors were part of the feature they may be no big deal to leave out, but the extra wires to add them would be trouble considering they all go through the dash. I'd avoid the mirrors if they happen to be part of the memory system.