I forgot Reynolds Oven Bags ... I have had great success with them in Altoid-sized kits.  They hold 2-3 liters of water and pack down REAL small!  Still nothing beats a condom removed form the factory package for a micro kit.  That what is in the handle of my CRK shadow (which is micro kits size for sure) and also im my other (standalone) micro kit which I have just finished. 
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Learn to improvise everything.