You can make them yourself fairly easily by buying full sheets of seaweed in bulk at an Asian grocery store (some regular chain grocery stores carry them too). The big packs of seaweed do still contain plastic, but it’s less than in a single-serving container. “Roasted seaweed snack recipe” will get you lots of google hits. Here is one link: https://www.myrecipes.com/recipe/sesame-seaweed-snacks
They do need to be stored in a VERY airtight container. The single-use seaweed snacks I’ve purchased always had something similar to a silica gel packet and an absorbent napkin at the bottom as well, so if you won’t eat this right away those would be good to add to the storage container.