Ace Hardware sells a Rutland replacement stove gasket kit (choice of 5/16" or 1/2" diameter) that comes with a tube of cement for $12. I've been having the same issues as y'all and wanted to seal the lid up. But like Mdboatbum said, make sure you put some decent holes in the lid. I put (3) evenly spaced 3/4" holes on the top of the lid, and have some old flexible rubber refrigerator magnets that I use to cover them so they're "infinitely adjustable". Works fine, but with the gaps around the edge, and how warped my lid and body are, it's not solving the problem completely.
I was worried about the magnets initially and whether they would melt/drip, but I had it up around 400° with no food in there, and they were good to go. Been traveling lately so I haven't had the chance to try it all out with the gasket yet, but hopefully I'll be able to this weekend.
PH