Your search for "ma-ant-mx" revealed the following:
NEW Cisco Meraki MA-ANT-23 2.4GHz 11 dBi Sector Antenna for MR74 and MR76 APs
SKU: NSN-8233
Condition: New
Shipping: Overnight Options
Warranty: 365 days
Cisco Meraki MA-ANT-3-F6 6 Port Narrow Patch Antenna for MR53E and MR46E
SKU: NSB-4086
Condition: Seller refurbished
Shipping: Overnight Options
Warranty: 365 days
NEW Cisco Meraki MA-ANT-3-B6 Dipole Antenna (Pack of 6) for MR46E and MR53E
SKU: NSN-0790
Condition: New
Shipping: Overnight Options
Warranty: 365 days