Build a steam distiller for 1 liter of water, in 316 stainless steel. Max weight 2.5kg, include plans for building another one, no jug needed, space for standard charchoal filter where water will drop out.
Similar to this, but smaller: [login to view URL]
Basically, a container to fill 1 liter of water in, and below the container is a built in heater to make the water steam, then on top there is a round pipe with cooling, a fan and an exit for the steam (now fluid) to drip out.
There should be a button to start it, and it should automatically stop when there is no more water to boil, or probably by the internal temperature, you figure out what's best and let me know.
Please see above link illustrating a 4 liter model.
Any questions, please let me know.
Please let me know how much you would charge for this as well as how long it would take.