the problem with a sardine can is that you can't really boil enough water in it, when you need it...

how about this?
http://mysigg.com/store/sigg-accessories...-box-green.html

i use this one:
http://mysigg.com/store/sigg-accessories...ge-box-red.html

its a bit big on the carry size, but it contains everything i might need, and fits into a cargo pocket.