You can find sour cream in coop and Migros, it's called séré à la crème, in coop it comes in a small container that is white and orange, near the quark section normally. It really is sour cream and not the runny stuff.

You can buy shredded cheddar in the Aligro in Ecublens, over by the shredded mozzarella and grana padano. Seems to me for chili it would do the trick. I use it for enchiladas.