Exhaust bolts for 147 GTA

[Kay_147_GTA]

Anyone know the best place to get replacement exhaust bolts from the centre sections?

We stripped the bolt heads getting the exhaust off to change the gear change bushing and now the exhaust is making a terrible rattle when cold. I believe the exhaust is not centered and / or bolts are loose and would rather swap them over to good ones when I take it to be looked at.