Side step fixings

I've taken the folding side steps off my 90 this afternoon to repaint, and one of the bolts is completely seized into the step. The nut came free easily enough, and there was enough movement to get the step off, but the bolt itself remains completely solid as if it's welded.

Anyone know if these bolts are available as spares? A normal bolt won't do the job as there's a much wider bearing surface.