Looking to buy Zinc ore, zinc concentrate

Looking to buy zinc oxide ore, or concentrate:

Must be oxide (no sulphide ore)

Capability: >15,000 tons per month

Spec:
>15% Zn for ore
>40% Zn for concentrate
Must be low of Iron (<5% Fe)

Supplier must be able to demonstrate ability for continuous, uninterrupted supply.   
Period: >18months (depending on supplier capability demonstration)

Price: CIF to the Port of Luderitz, Namibia

Payment term: Irrevocable LC against agreed analyst report at sight