Hi Wil and welcome to the LOC.
Apologies for the late reply.
One of the many good things about Lexus cars is, as you have already discovered, they tend to fit the full wiring harness to all models so retrofitting heated and electric seats is generally “Plug and Play”
Obviously you would need to source the seats, switch panel and maybe fit an extra fuse or two but they are basically 4 bolts and a couple of connections.
A wiring diagram would be useful and usually found from a search.
steve2006's post in IS200 Knock Sensor was marked as the answer