alternator mount bolts breaking

the long bolt that goes through the bottom alternator mount on my rs2000 broke long ago, and i could only replace it with a couple shorter ones. these keep constantly breaking.
i can tell when they've broken because my fan belt begins to whine. is there some sort of strengthened aftermarket assembly you can buy to prevent this?
i can tell when they've broken because my fan belt begins to whine. is there some sort of strengthened aftermarket assembly you can buy to prevent this?