I found some 200mm heat spreaders at a kitchen store.  They consist of heavy wire circle with a steel screen inside the circle.  They work great on the Westfalia stove and on the propane stove we use on the picinic table.  The brand name is SIMAX, they were made in the Czech Republic, I bought them at a Paderno store for $7.80 cdn. for a pair.
George
'85 Westfalia