Have you considered a chair that supports your posture? Or try rolling a towel and placing in along the mid-line of the spine to open your heart and drop your shoulders back. This helps posture quite a lot. To practice, you can start laying on your back with the towel along the spine. Just relax and breathe there for 10-15 breaths, and then try sitting.

Let me know if you like it...I've got a lot of tricks up my sleeve!

oh nah, im after a brace. thanks.
anyone else?

A brace can be helpful. You can get a standard lumbar support at a medical supply store. the only problem with a brace is that after a while your tummy muscles will become flaccid from using it. Their job is to be strong so that you can hold your posture without the use of a brace. So you could use it for prolonged standing or sitting, but you would want to be sure to use it for only a few hours a day and make certain you do a lot of really good core strengthening work to help save your back. Also, if you stand ona hard floor, be sure to put a padded mat under your feet. Another thing that can help is to put one leg up on a stool about 18 inches high, and then alternate to the other leg every 15 minutes or so.