I think they actually sell dehydrated sour cream, although I've never tried it personally. Seems to have reasonable reviews on amazon

Amazon: Sour Cream Powder

Guacamole I don't know about, how calorie dense are avocados? grin

Balzaccom, that sounds pretty good, I hadn't even thought of just chopping up a burrito and dehydrating it. I'll have to try that.