Your search for "ex4300-fan" revealed the following:
Juniper EX4300-48MP-FAN EX4300 Series Front-to-Back Airflow Switch Fan Module
SKU: NSH-9693
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
NEW Juniper QFX5100-FAN-AFO F-B Switch Fan Module for QFX5100 and EX4300 Series
SKU: NSN-5908
Condition: New
Shipping: Overnight Options
Warranty: 365 days
Juniper EX4300-48T-DC 48x 1GB RJ-45 4x 40GB QSFP+ F-B Airflow (DC) Switch
SKU: NSH-4915
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days