You don't need a substitute for Cheddar because you can buy it at Migros. Just take a close look. It is in white cheese paper like all the cheeses, comes in about 300 gram blocks, it has brown text on the label.

Also, you could try Manor grocery floor for real Sour Cream. I would also consider using philedelphia cream cheese as a substitute. It is great on baked potatoes, as well a lot of N. Americans use a high-fat plain yoghurt as as weight loss subsitute for sour cream.
Probably with CHile the yogurt is better.
Also the creme fresh sounds good.

Good luck.