Ebay is your only hope. Suzuki made all sorts of orphan bikes, and getting parts is not easy for them. At least you have a '72, and that's the one bike that's easier to get parts for.
My front fender on my '74 cracked, and I had to drill holes on each side and "stitch" it back together with a piece of picture hanging wire. I then used a Fiberglas repair kit to lay some mat on it and weld it together.