With the furnace cold, I removed the broken lid and had a look.
The metal is actually thick sheet metal, and in good shape, so no change needed. The brick lid was broken into four pieces, so was discarded.
The new lid was about 1/2 in too long as was the last lid, so I cut the new lid down to size, and now it fits perfectly without distorting the sheet metal. I cemented the cut face with two coats and cured it in the annealer at 100F. I then installed it in the metal frame. As it turns out, painting the fame clogged the fastening clamps, making it very difficult to properly secure the brick in the frame. In the end a set of pliers and a ratchet got the job done.
The furnace is clean, crucible vacuumed out and all is ready to go hot.