I recently purchased an analog hygrometer at petsmart that can be adjusted! (Yep, its the little things that make me happy, LOL) It made by All Living Things
http://www.petsmart.com/product/index.j ... Id=2752691
On the back of it there are a few small holes, the hole in the middle is slightly larger and you can see a metal piece with a slot in it that would fit a screwdriver. You can use a small screwdriver to adjust the gauge
I think most hygrometers are not accurate when you buy them and the better ones are the ones that you can adjust without much difficulty.