Sorry, I missed the Polly tank. As rick suggested check out Mohler. They have dimensioned drawings on their website, and then I’m sure West could order whatever you want, though you’d save a bunch buying it on amazon.
The only think about Polly tanks is they come in a limited range of sizes and configurations due to the expense of making the molds. I found a 56 gal Mohler tank that would have fit in my CCP, but the fill/pickup were in the wrong place. Ended up with custom aluminum instead.