here are some drawings of the main parts. these are the only parts you have to manufacture or let some metal shop make them for you.
in my first prototype I used aluminium, it appeared to be not perfect. Aluminium takes out the heat of the water way too fast. It is actually a lot better to use stainless steel, that has a lower thermal conductivity:
aluminium: ~ 236. (it cools down the hot water very fast)
stainless steel: ~ 20 (it keeps the heat)