The quick and dirty fix of trying to repair a missing/damaged pin in a CPU or hard disk is to use a similar gauge piece of wire (in this case, a paperclip), poke it into the end of the SCSI connector, plug it in and hope for the best

50-pin SCSI hard disks seems to be pretty common still, unlike their 2.5" counterparts. 68-pin cheaper again and more plentiful, but not all work with the standard 50-->68 pin adapters.