Rik, the heat Pal replacement canister looks like it could be made from a large flat tin ( ? a steak and kidney pie tin , pie removed through smaller hole in top ..... perhaps packed with glass fibre and the vent a bit of wire mesh ?????
Toddy maybe I should play safe, I have one of those flat stoves, could the radiant heater addition be improvised out of a few old tins inserted inside one another and bolted +++ some perforations/ventilation holes drilled?
The old terracta pot idea sounds nice will go and search for that, maybe the steak and kidney tin idea and an old clay pot ontop.......