1.5" plug

We have chickens at our house and have tried various watering devices. What we currently have is the 2-Gallon Rent-A-Coop watering bucket. This is working well so far, but we almost immediately lost the plug for the top (to keep dirt and bugs out). The hole diameter is 1.5". Instead of buying a replacement for about $3, I designed this and printed one out - it works great. The middle is 1.5" but it has a 10 degree slope so it's slightly wider at the top and narrower at the bottom.