well you have 2 options. 1) replace that bolt/tensioner. 2) get a smaller belt.
do you use ur A/C? if not, you can get a smaller belt that will bypass the a/c pulley and that tensioner pulley. it wraps around the alternator, upper idler, and crank pulley. easy to install, i can give you more info and belt part number and such if you need it.
i recently put this aforementioned smaller belt on a guy's 3S. his A/C pulley was vibrating annoyingly loud, and since he didn't use the A/C, we just bypassed it. SO, i have this guy's tensioner pulley (since he has no need for it), the one in question that you broke. if you can just pay shipping, i can mail it and all the associated parts to you (pulley, bracket, bolt that you snapped, and other bolts). it works great, i even took it apart and cleaned it. however, if you want me to polish it, that will be extra. polishing is worth about 10hp, by teh way.
