Where can I find sheets of plastic that are at least 25'; x 25';?

I am looking for the non-corrugated kind. The sheets need to be solid plastic and have a thickness of no more than 1/4';. Thank you!Where can I find sheets of plastic that are at least 25'; x 25';?
If you happen to live near NYC, there are stores on Canal Street dedicated to selling plastic products and they sell plastic sheets.Where can I find sheets of plastic that are at least 25'; x 25';?
Home depot