I wouldn't think a aftermarket company needs to be involved. Should be able to splice light wire on the mirror, into the turnsignals. probably have to cut the wire in the mirror , I assume it will backfeed into the parking light circuit otherwise. I have a post about heated mirrors in this forum. It details how to disassemble the mirrors and doors. Other than locating the turnsignal wires, it should have all the info you need. When I get a minute I will look at the wiring schmatics and post the colors and locations. Check back.

P.S. a quick way to accomplish this is to use a 12volt probe, and check at the lights themselves. Determine which are the hot wires, when signals are turned on. They USUALLY don't change colors. Then look on the main harness on the steering colum, and see if you can locate same color wires. Retest with your probe, if they flash when signals are on, you found them.