what color are you looking for? On ebay you can find race seats of all kinds of colors for $220 and free shipping. for another $40-$60 you can also get the heating pad elements.
Install them like this and you've got some nice new heated seats for under $300.
And if I were you, I would dismount the new back seat and bottom seat from the bracket frame and install them on the stock lexus brackets and frame. This way you can still keep the electronic adjustability option of your seats. The only thing you will lose would be the adjustable lumbar support inside of the stock back seat.
hope this helps.