Hi,
I was looking at the datasheet for the c1852E access-point, and i could just see one compatible patch antenna for this particular AP, AIR-ANT2566P4W-R=.
I am looking for something with a narrower beamwidth. Is there such a thing available for use with this AP?
Have a look at the AIR-ANT2566D4M-R antenna.
Otherwise, take a look at https://www.cisco.com/c/en/us/products/collateral/wireless/aironet-antennas-accessories/product_data_sheet09186a008008883b.html
For Cisco Antennas.
Other option would be to look at other vendor-neutral antenna vendors like:
Neato