Front passenger seat

Information on this is rather sketchy. The Lexus ES shares the same platform (maybe) with the Avalon. You could try to swap seats but no guarantees.

Unfortunately the ES of the same generation have basically the same seats as the Avalon. Really flat lack of bolsters hurts my kidneys diving hard into a turn. Sigh. It's gonna be a custom job if it happens at all. I thought about getting the OEM lower and seat back cushions from a newer Lexus IS and seeing if I could tear my driver's seat down and transplant the cushions from the IS. Not that they are similar inside, I don't know that, but they have great bolsters. Any Avalon seat swap will be a custom job, some kind of adapter bracket, rewire and/or mix and match electronics, etc. ECU will be angery with you if you fail to satisfy the airbag connections