Hey So I bought a set of Oxford "Heaterz" Touring Grips a few years ago looks like it may be a discontinued item.
The Sportz instead of the Touring may still be an option:
Oxford Replacement Heaterz Sports Grip - RevZilla
But not sure if you read on the forum, there's a few writeups on how to add an aftermarket plug to the factory prewiring!
You have to have a dealer or shop activate the grips (you can do it before you actually install anything which is what I did when I was there for a service and then installed them months later)
It's built in to the Hyperstrada from what I can tell. It for sure was on my '14 HS 821 so I'd imagine the same on a 13.
The cool thing is it's cheaper to buy because you just buy the "replacement grips" without a controlller so they're cheaper and it looks completely factory without a switch.
It uses the starter button once started it toggles between OFF LOW MED and HIGH.
The Oxfords work PERFECTLY and only on days when it was 0 degrees in the mountains did I ever need it on High even with regular non-insulated gloves. Super Hot. Awesome not needing to worry about winter gloves either.
There's the specific plug that Ducati (forget the name) uses that you Cut and splice onto the grips and then they plug in without cutting anything on the bike.
Should be 2 prewired ports one for GPS and one for heated grips on the HS.
Hope this helps!
The Count