I use an office chair. I rolled up a bath towel and used a bungee cord (with some improvising) to attach the roll to the chair so that I have support on my lower back. Once in a while I have to relocate the towel so it correctly fits into the small of my back. The support feels great. A physical therapist advised I do this and save myself the expense of a special back support.
Also, when I'm at the computer, I use a dining room chair with a back support I GOT AT THE DOLLAR TREE!!! Guess how much I paid for it? Ha Ha Ha.