I called an aftermarket company who sells the battery operated units as seen here:http://www.opendoorsandmore.com/Talked to a lady on the phone - very nice and very helpful. I didn't realize that HomeLink is somewhat limited in how they're sold. Apparently - they (HomeLink) don't want the average JOE DIY'er buying and installing these things. There's only a few ways you can get them outside of your OEM or factory installed units.... The mirrors, sunvisor mount, and battery operated units. That's it..... They don't sell just *the box w/ buttons* and the average joe can't buy them (only installers).www.toyotanation.com
At the dealer since it is probably under warranty and ANY modifications to the vehicle can void such warranty.