Plastic stake hole covers for my 72 pickup

[bvb69C10]

Does anyone know where I can get plastic stake pocket hole covers for my 1972 short bed fleet side pickup.I found an old thread that led me to stainless metal caps but I'd prefer plastic. I've searched the Internet without success.I want to add a tonneau cover but the only covers that actually cover the holes are fiberglass and pricey so I'd like to cap the exposed holes. Any help would be greatly appreciated.