I google free pallets and got this:
Here are ten sources for free, clean pallets:
Bars and craft beer locations
Pet food stores
Feed & Tack stores
Stationary shops
Furniture stores
Liquor stores
Schools
Flooring stores
Other small retail
Construction sites
The worst they can do is tell you no. I work in printing and know that most of our pallets either get taken home or tossed out. Most grocery stores reuse their pallets but maybe not major chains. I used to work at a local store and we reused them until they fell apart.