Square? Sorry. I'm no help there. But round...

I haven't put one to use yet, but I bought a couple of MSR Stowaway pots with the idea of turning them into car kits. They come in various sizes, have a handle that locks the lid shut (though not waterproof) and are honest-to-gosh real pots.

http://www.msrcorp.com/cookware/stowaway_pots.asp

I don't know how big the Esbit stove is, but it might fit in a Snowpeak or Varago titanium mug.

http://www.prolitegear.com/snow_peak_titanium_trek_700_pot.html

http://www.prolitegear.com/vargo-titanium-mug.html

(These both fit over the bottom of a nalgene bottle, by the way.)

Bear
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No fire, no steel.