The phrase "additional commodity" is correct and usable in written English.
It can be used when referring to an extra item or product that is added to a list or inventory.
Example: "The store has introduced an additional commodity to its inventory, which is expected to attract more customers."
Alternatives: "extra item" or "supplementary product".
The parents were encouraged to obtain additional commodities as the case may be and seek care in the event of failure to recover from diarrhea.
That bill gives less money to conservation and nutrition programs, places no limits on individual subsidy payments and gives an additional $9 billion to commodity subsidies over a decade.
The shallow seas of Island Southeast Asia suddenly had an additional valuable export commodity enabling local communities to contribute to these networks.
Because the utility yielded by each additional unit of a commodity usually decreases as the quantity purchased increases, and because the commodity's price reflects only the utility of the last unit purchased rather than the utility of all units, the total utility will exceed total market value.
But their critics say the additional cash they bring to commodity markets artificially inflates prices to the point that they are detached from fundamentals like supply and demand.
It might seem odd for a star with seven majors to feel the crush of the moment, but counting each additional opportunity as a precious commodity, Agassi could not sustain his concentration past the 13th game of the fifth set.
In the same bulletin, it warned that the first "critical pipeline break" in its Syrian operations was expected in January 2015, adding: "Considering commodity lead times, additional resources must be secured by early November to ensure procurement and arrival of supplies in time for January distributions".
The marginalists based their explanation of prices on the behaviour of consumers in choosing among increments of goods and services; that is, they examined the benefit (utility) that a consumer derives from buying an additional unit of something (a commodity or service) that he already possesses in some quantity.
While other commodities like oil and copper also guard against inflation and may have more room to grow, gold is the only commodity to offer additional protection against deflation.
