I've never heard of one for a Duramax. There are some good diesel aftermarket retailers like Thoroughbred and PPE, among many others. Maybe check those sites out.
May even give them a call. They have some great products and diesel techs. If they don't sell it they might know who does.
As Axe stated you can buy an aftermarket timer that shuts the engine off at a pre-determined exhaust temperature. Banks is a good on as well. Several years ago we installed one on my friends Cummins that we did a bunch of work to. At first it was weird to walk away from the truck with the engine still running, but he got used to it. I believe we set his to turn off the engine at 400*. Diesel exhaust cools fairly fast at idle.
I used the Edge CTS product with the timer on my 2015 RAM and it worked great. It appears the CTS3 will work on the Duramax as well so I may go the same route. I do like the compact style of the Banks Idash gauge but it doesn't appear to support the timer feature. it's nice to just walk away from the running vehicle and not have to wait for temp to wind down which on a hot turbo could be 5+ minutes.
We used the Edge unit too. The truck was a 2001. We turned up the timing, fuel and replaced the turbo exhaust housing. We then ran a 5" exhaust to the rear of the truck. That truck was a monster going over the mountains, with his camper on and an enclosed MC trailer in back with two bikes. He literally would let off it a bit at the top of Vail Pass, running 80 MPH. He kept the EGT's ar 1200 F* or less so it was pretty safe. The fellow that bought it loves it! It's kind of hard on the old 47 RFE, though, LOL!
