Yea just ask your local grocery store. If you know anyone that works there then they may be able to snag some for you.
I get my cardboard egg flats from work. Funny story: i told my friend what they were for and how i was breeding dubias to feed my T's. He got grossed out but then like a week later hes like "so how is your breeding going? Are the snakes eating the tarantulas?" I was like "um... What? No the roaches are to feed the tarantulas, and thats where the food chain stops lol..." He thought i was feeding T's to my snakes. When he realized i just had the T's as pets too he freaked out even more hahaha.