Forget the special chair and start workout, walk and stretch out every morning. Your back pain is an indication that you miss those things and instead of hiding the problem you can reduce it.
A good chair is good of course, but it's not everything. I worked a year on an old wooden chair that was closer to break down than my body and with this strategy I never had any back problems.
If you are still looking for a chair Kinnarps make some very good ones.
But one hour walk every day and a little bit of back stretching and you will feel like a new person with much more energy to work too :-)