While it may not be a pocket-sized solution, how about a pouch-sized one such as a mini bread tin? Look at this:
http://www.amazon.com/Set-Mini-Loaf-Pans-Inch/dp/B002UF8YCY .
Those could fit in a small MOLLE or similar pouch. There is a guy who built a "survival" kit out of one.
Standard Disclaimer, YMMV, IMHO