Your search for "qsfp-40g-sr4" revealed the following:
Nvidia Mellanox MC2210411-SR4L 40GB BASE-SR4 850nm DOM MMF QSFP+ Transceiver
SKU: NSB-6813
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
$ 91.99
• Only 2 remaining
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Arista DCS-7500R2-18CQ-LC 7500R2 Series 18x 100GB QSFP28 Switch Line Card
SKU: NSB-7177
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
$ 2,029.99
• Only 1 remaining
Call if you need more
NEW Arista DCS-7500R2-18CQ-LC 7500R2 Series 18x 100GB QSFP28 Switch Line Card
SKU: NSN-9203
Condition: New
Shipping: Overnight Options
Warranty: 365 days
$ 2,056.99
• Only 1 remaining
Call if you need more
NEW Arista QSFP-40G-SR4 40GB BASE-SR4 850nm Short Reach MMF QSFP+ Transceiver
SKU: NSN-1701
Condition: New
Shipping: Overnight Options
Warranty: 365 days
Juniper EX-QSFP-40GE-SR4 40GB BASE-SR4 850nm MMF QSFP+ Transceiver
SKU: NSH-9719
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
Cisco Meraki MA-QSFP-40G-CSR4 40GB BASE-CSR4 MPO12 850nm MMF QSFP Transceiver
SKU: NSB-0840
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
NEW Cisco Meraki MA-QSFP-40G-LR4 40GB BASE-LR4 1310nm SMF QSFP+ Transceiver
SKU: NSN-8323
Condition: New
Shipping: Overnight Options
Warranty: 365 days
NEW Cisco Meraki MA-QSFP-40G-CSR4 40GB BASE-CSR4 MPO12 MMF QSFP Transceiver
SKU: NSN-8324
Condition: New
Shipping: Overnight Options
Warranty: 365 days
NEW HPE JG325B 40GB BASE-SR4 850nm MPO QSFP+ Transceiver
SKU: NSN-7207
Condition: New
Shipping: Overnight Options
Warranty: 365 days
Cisco Meraki MA-QSFP-40G-LR4 40GB BASE-LR4 1310nm SMF QSFP+ Transceiver
SKU: NSB-0838
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days