The organization that does the Forward Seat method is the ANRC (http://anrc.org). They seem to mostly do their stuff through colleges, but they may be able to give you leads for lesson programs where you are.
I am so sorry you have MS too. If there is any way I can help, at least encouragement, let me know!
I restarted riding after 5 years of just being too exhausted to ride. I found 2 stables down here whose ladies are helping me ride. They have to catch, groom, tack up, cool down, untack and put the horse out. I can only ride about half an hour at a time, usually I get to ride three horses a week, for a hour and a half total riding time. Luckily I had my own horses for decades so I knew how to ride.
GET BACK TO RIDING!!!!! Riding horses is the only reason I am still walking. I wore out an electric wheelchair, now I am walking with two canes, but after almost 5 years since I restarted riding I NO LONGER NEED A WHEELCHAIR OR WALKER. For us, people with MS, riding is the secret to eternal youth AND much better as physical therapy that anything else I've run into. One thing that really helped me was that I can practice losing and regaining my balance on horseback without falling down. My balance is sooooo much better now!
Most of my blogs are about riding with MS, my problems and the solutions I come up with. I hope you enjoy reading them, you may find things in them that will help you when you get back to riding. Feel free to comment on my blogs and feel free to ask me questions any time. Us MSers face challenges that few other people face, and believe me I will never consider a question dumb. Hey, just lately, I can no longer dismount from one of my saddles, thoroughly humiliating (plus the first time I was on an 18.2 hand horse), but I've figured out a way to get down safely.