There’s a thread I remember reading a couple years ago about installing an aftermarket heated seats kit, with switches that fit the blanks. The kit was less than $150 online. The thread had a how to with plenty of photos. Looks easy and I’d love to do this on my ‘18 SR5, but removing and replacing the upholstery looks above my pay grade, so I haven’t jumped. No upholstery shop in my small, isolated town either.