Where can I buy a small piece of chicken wire (12"x 12")?

hardware store

Ace hardware r any hardware store ,,lowes ,,,home Depot. ..

May need to buy a roll.

I'd check around your local hardware stores first. Get on the phone and start asking. Believe it or not another source is craft stores, although you'll probably pay more. After you've done some "phone walking" and if you have a Habitat for Humanity Restore in your area, try there. Also garage sales if you like to do those. I spent hours yesterday at a multiple family neighborhood garage sale event and saw all kinds of things! You never know what you'll find, but chicken wire is not out of the realm of possibilities.

Good luck!

Try Amazon and Michael's online. I've purchased small amounts from both.