Your search for "MMA4Z00-NS400" revealed the following:
NEW nVidia Mellanox MMA4Z00-NS400 400GBASE-SR4 850nm DOM MMF OSFP Transceiver
SKU: NSN-0230
Condition: New
Shipping: Overnight Options
Warranty: 365 days
$ 925.99
• Only 2 remaining
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nVidia Mellanox MMA4Z00-NS400 400GBASE-SR4 850nm 50m DOM MMF OSFP Transceiver
SKU: NSB-4265
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
$ 887.99
• Only 2 remaining
Call if you need more