The government has reference products that a lot of processes use. https://shop.nist.gov/ccrz__ProductList?categoryId=a0l3d0000...

one that gets mentioned occasionally on the internet is the peanut butter: https://shop.nist.gov/ccrz__ProductDetails?sku=2387

I was more imagining a completely pedestrian sourced sample. Those are likely large aggregate pools to minimize heterogeneity. Looking for something like, “Go to corner store, buy 12 pack canned CokeCola (with aspartame), dilute 1:10, measure”