If the vice grips didnt work and nackers idea didnt work then one of those stripped bolt tools wont work either. What we used to have to do when we had rusted/ seized bolts on our bikes was to use a dremel and a cutting wheel. Cut the nut off. Cut vertically on the nut from top to bottom. you probably wont be able to cut all the way through without hitting the threads, but thats ok. Cut as much as you can and then get a big burly flathead. jam it in there and hit it with a mallet. The nut should snap off. Then you will have to buy a new one of course... lol

Good luck

Hit me up on IM if you need more directions.

-Chris b.