The best fix for a mosquito bite is to not get bitten! But once you've been bitten, the second best fix is heat.
If you can heat the lower layer of the skin to 42 degrees celsius for 5 seconds, that's usually enough to break down the chemicals it injects that make the bite so itchy!
A very quick soak in a natural hot spring, is wonderful for this. But I also a very hot shower to do the same.
Well now, I've managed to find a little portable machine to do this. It's a heat lamp I found on Lazada.co.th. It's battery powered, you place it against the skin, turn it on, count to 15 (or 5 second after you feel the burn), and the itch goes.
It doesn't fix any disease you've been injected with, so mosquito bites can still give you dengi fever, but the itchiness goes.