Aftermarket SKS?

I can't believe no one's responded...

Sorry, but I don't think it's possible.
I'd say it's as expensive as buying another Prius with the SKS option installed...
So when you trade it in, look for that option.

Mine doesn't have it and as much as I'd like it, think about this:

You're in a hurry and you think you have your keys in your pocket (but they are really somewhere in the kitchen) you rush out the door and get in the Prius, press the power button and it starts up and runs fine (the transponder picks up the signal from the keys in the kitchen).

You drive to work, or the mall, or where ever your off to... you get there, you turn off the Pruis, step out of the car and reach into your pocket to lock the doors only to discover that you don't have the keys! you try and restart the prius, but it won't start because the transponder is now out of range. you try and lock the doors, but you can't lock them... Hope you have a cellphone and a loved one at home or a good friend that can get into your house to retrieve the keys and deliver them to you!