Today I bought a water boiler from Tefal. More exactly model KI150. Unlike the rest of the water boilers this one has no transparent plastic window to look into to see the level of water. Instead it uses still a plastic stopper mounted inside near the pouring opening which simply states MAX. The good thing about not having a plastic window to look into which all the other models I have seen so far has is that the 100 degrees boiling water doesn't touches with the plastic while it boils which I don't think is healthy.
In fact I wasn't out to buy a water boiler but to buy an adapter plug to use for the water boiler at work, which is made for the UK network and thus incompatible with the ones in here. But the adapter I found was almost half the price of the water boiler and I wasn't even sure it would be good as it was not clear from use instructions.
So I bought the Tefal which I happen to find at the exact same shop.