I have a 1997 saab 900se and the bolt the holds the tensioner assembly snapped off.how much would it cost?

when i was trying to remove the tensioner assembly i guess i was turning the bolt the wrong way instead of loosing it i was making it tighter and since i was making tighter it snapped off. I did not know i snapped the bolt until the tensioner assembly came off and i looked at the bolt. now there a pease of the bolt still on the hole where the bolt needs to go. i dont want to take out the bolt my self so i want to take it to a pro to do it. how much would it cost to remove that snapped bolt