Ian,
as a more realistic alternative are you aware of the Remoska [2L standard size]? This is a favourite amongst Eriba owners. It will basically cook anything you in an oven that you would at home. They are pricey from Lakeland but excellent used examples are available, better Gumtree than e-bay, for about £50. We have a newer one at home but the one in the van is 20+ years old.
Colin