I don't remember the brand, but I bought a very cheap reptile hygrometer from our local PetCo when the fancy, more expensive one I bought online turned out to be horribly innacurate.
I paid about $6 for it and it is right on--very reliable! And it is brightly colored and easy to read through the 'bator window. I also bought the matching cheap-o thermometer for my brooder, though I wouldn't trust that in the 'bator!