check out panavise in dash mounts. I know they make them for 4runners. Here's a link to the site
Panavise
I'm not really sure which one you're looking for, but they have several. It's essentially creating a bracket right near the Heat/AC controls. Good Luck.
FWIW, I installed mine in my cupholder of my old Acura. I am currently trying to find a method of installing it in my 4runner as well. My acura had 3 cupholders for the front seats, so I could give one up. With the 4runner only having 2, I'm looking at the Panavise mounts as well.
