The Memphis and Cookshack offer insulated lids.
David, I thought about the potential benefits of pit insulation when I bought my Cookshack Fast Eddy PG-500, which is not insulated. Cookshack makes an insulated model, the PG-1000, but it's $1,200 more. I thought, "The PG-500 will maintain temperature, it wil just burn more pellets. Well, $1,200 will buy a lot of pellets. The time-value of the money not spent will result in more than $1,200 savings."
So I bought the uninsulated model. YTMV (thoughts)