Your search for "QSFP-40G-ESR4" revealed the following:
Juniper QFX-QSFP-40G-ESR4 40GB BASE-ESR4 850nm MMF QSFP+ Transceiver
SKU: NSH-9694
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
$ 105.99
• Only 2 remaining
Call if you need more
Dell QSFP-40G-ESR4 40GB BASE-ESR4 Extended Short Reach MMF QSFP+ Transceiver
SKU: NSB-5938
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
NEW Juniper QFX-QSFP-40G-ESR4 40GB BASE-ESR4 850nm MMF QSFP+ Transceiver
SKU: NSN-3404
Condition: New
Shipping: Overnight Options
Warranty: 365 days