Like this? It's not a long term fix, but this fix will get you out of a hole until you get a new boab. Get a large screwdriver and prise the rivet off. Then drill a bigger hole if need be. Get a bolt and 2 nuts. Hacksaw the bolt so it doesn't stick to far into the boab. Get the 2 nuts and screw onto the bolt. Don't tighten the nuts up to the plastic, as you want it to swivel. Screw the nuts tight and against each other so they won't work loose. You will also need 2 washers, to stop the screws and bolt working its way through the plastic.