Front fork panniers add too much drag and weight on the forks, really a bad idea. On bicycles you can get away with it somewhat...the steering is very heavy and in some ways it stablizes the steering but that delayed steering can be a problem if you want to avoid a pothole or stone or chunk of metal unless you see it really early. Tough to stablize the panniers in the front as well, any jostling back or forth can be hard to control in turns.
You looking for rear soft bags, there are several brands, A Moto___ brand out of Canada, Cortech, Aerostich, etc. You will probably have to fabricate your own pannier frames to mount the bags to and keep the bags out of the rear wheel/shock coils.
David