I really don't think the heated steering wheel is an option on a 4Runner. Here is the official Toyota brochure which includes all the standard equipment and options at each trim level:
http://www.toyota.com/content/ebrochure/2016/4runner_ebrochure.pdf (scroll towards the bottom to see the feature matrix by Trim).
The Highlander *does* have the feature available with the "Platinum" package on the Limited line:
http://www.toyota.com/highlander/ebrochure
There are a few aftermarket heated steering wheel kits but it looks like they're all pretty janky. You could also look into getting a remote-start kit if cold mornings are a problem.