A few months ago I was in the Parker Costco looking for bags of salt. Spoke to an associate when I couldn't find any and he told me to visit the Costco Business Center. Have yet to go there but expect it to be there. They furnish supplies for restaurants and no restaurant is going to buy salt by the ounce, they'll buy it by the 5 gallon buckets.
from what I saw you didn't need a business license to shop there neither; just regular membership.