Maybe go to Home Depot and look at pipe flanges. Take a piece of paper with a trace of the hub on it, find a flange, get a couple of stainless steel bolts to hold them together. If there are no flanges that match the prop hole for hole (probably not), get a large PVC flange and drill a suitable hole pattern. Maybe paint the flange flat black. If the prop is heavy you are going to need to drive a big lag screw into a wall stud to hold the flange/ prop up there. Good luck! Great fun.