Rice cakes? I find them indistinguishable, in both flavour and texture, from those biodegradable plates you can get made from potato starch. (Yes, you can eat them, and yes, I have actually tried it.)
Boursin doesn't cope well in your rucksack.
Malt loaf is a favourite of mine / tube of primula and oatcakes or biscuits of choice and squeeze primula over in large quantities, babybells as alternative to primula, small bread roll or fruit buns alternative to oatcakes / hard boiled eggs / eccles cakes / peperami / dates / jelly babies.