https://www.amazon.com/gp/product/B0064O8OYK

I can vouch for this exact product.

You need to make sure it is HDPE plastic. It should have the number 2 inside the recycle triangle thing on the bottom and say HDPE directly underneath it. Anything else and you might have a bad time.

If it's partially buried I don't think the insulation is necessary.

And HDPE will be more resistant than polypropylene.

https://www.amazon.com/5-Gallon-Plastic-Hedpack-cap/dp/B0064O8OYK/