The beef initiative has already done this, though it is only with beef. You may attempt to copy their model https://beefinitiative.com/

You may also consider Galoy's model since they did develop a merchant network for a circular economy (Bitcoin beach) https://galoy.io/bitcoin-banking-for-communities-lessons-learned-from-el-zonte/

Simple user experience suggestion, list by product type, not store name. Stores should be listed next to each other under product types. This is because I as the consumer do not first look at stores I've never heard of, but rather look first for product type, and then consider who's product of that type I may prefer.