A couple months ago, before I finally bit the bullet and purchased a quality desk chair similar to this one, I found this terrific back brace. It fits around your waist and a padded strap loops around each knee (clipping together at mid-thigh). The tighter you cinch the adjustable straps, the greater the pressure applied to your lower back. You still have plenty of forward movement, and the way it supports the lower spine is wonderful.
It’s a little pricey, but pays off immediately. For the past two years, I sat on a dingy secondhand chair at a low, makeshift desk (home office = a walk-in closet). The result? Regular slouching and hunching and frequent backaches, pains and stiffness, especially in the morning. The first day I strapped this thing on, I felt the difference — and I still use it whenever I head to the library or travel and I know I’m going to have a marathon desk session in less than stellar conditions.
There are a variety of models. Mine is an all-black “S’portBacker,” which was the cheapest one available at the time. I really enjoy how it folds and zips together into a convenient package (8 1/2″ x 6″ x 1″).
[Please see the previously-reviewed Slouch!Buster, which is the same product.]