Checked both of those and even called Pit Boss. They said it was coming soon. I did get the 25% off coupon after registering so that's still going on. For now just using a tarp.Try here and see if one of them will work.
When you register your grill Pit Boss normally emails you a $25 coupon (I think it is 25). I used it when I purchased my cover for my vertical.
Says it is for 820, don't know if it will fit the 850.
The touchpad is pretty sweet and very easy to use. Still can only increase temps by 25. The smokeit app works good too as it gives you current temp of the smoker and your meat probes.