There is a range of "portable" solar cookers ranging from fold-up to suitcase models:

http://65.108.108.197/catalog/solarcookerskits-c-1.html?osCsid=175170b8962102b1cfd38c77657d5c59

Here's a compact solar water purification unit:

Aquapak water purification system with built-in WAPI $20
http://65.108.108.197/catalog/aquapak-p-37.html?osCsid=175170b8962102b1cfd38c77657d5c59

If your bug out or other travel is at night, and you are going to hole up during the day to sleep, eat, and minimize detection, then a solar cooker might be a good fit. If your day will be spent hunting, fishing, and foraging away from a base camp or survival retreat, then a solar cooker makes good sense. Edit: except in bear country I guess you might want to use unattended solar for purifying water only.