I got a pair of folding camping stools to cure that. If Asda are still doing a stock clearance, you can pick up a pair for four quid. They're stronger, comfier and lighter than they look, and even have their own carry bag with shoulder strap.
BTW, I only sit on one at a time. My arse isn't that big.
Nice, I'll keep an eye out for those. I think the army-navy shop has some too.