EJ 25 crankpulley bolt thread size??

[rebuilder]

Ok, lent my 2000 outback to my mate for a couple of weeks, and sure as hell, while he had it the harmonic balancer (crankshaft puller) managed to undo itself and go under the car and off back down the road causing my mate to drive home with no air-con, power steering, or alternator!! Some guy apparently yelled out , HEY MATE YAH CARS FARKED!! lol

now ive gone n splurged 380 bucks on a new pulley for christ sake, and i have no idea where the hell to get a bolt for it!! I have rebuilt 5 engines and serviced many cars in my time, and ive never been stumped on something so stupid!!

anyone able to measure their crank bolt they have lying around?
Please dont tell me a bolt is a special part which needs to be ordered from subaru?