I haven't seen any made to fit. Looked at using welders blankets and fire proof felt but just wound up using an old thick cotton floor mat my wife had and it has worked well covering the top and front.
Too bad the Silverton lid sides are not double thickness like the Ironwood.
Hoping Traeger will make a blanket for the Silverton. Sure would help in the winter. I emailed Traeger directly, and they did respond. Just no commitment to make one. I encourage everyone to contact Traeger.