JRSC Tensioner bolt size

Hey guys, I snapped the manual tensioner bolt on my JRSC. The head snapped off, but is still being held in place by the lock nut at the bottom. The car is squealing so I want to replace the belt and check out the pulleys, but I don't want to take the bolt out to do so without having a replacement on hand. I've been searching for an hour or so now and can't find the dimensions for this bolt anywhere. If anyone can measure one for me, or knows the dimensions off hand, I'd be super appreciative.

Thanks much.