You can use a closet screw on the broken side of the flange. It will require drilling a hole in the floor beneath the broken part of the flange if it is not wood and using a plastic or lead type anchor. You can also use a Spanner Flange to compensate for the broken section. Most large home supply stores will have this item or a plumbing supply house as well. MOE
Come on Moe! shouldnt he drill out the lead, replace the flange, pack it with oakum and pour some lead? OR get one of those cheesie INSTA-SET flanges with the grooved rubber? OK, I’ll shut up now.