you could possibilly get a good engineering works to drill out the hole to the next bolt size that will fit and tap a new thread in the clean hole. then a bolt could be turned down to suit the diameter of the original stud while retaining the thread for the new hole.and then its just a mater of cutting a new thread on the plane section of the machined bolt to take the nut for the bearing cap
i know it sounds like a lot of heavy work but its very simple to a good engineering works and a lot cheaper than buying a head. plus the bearing caps have a very light tightening torque so there is a very small load on an individual cap