#1800-60 (sko13e0460) has been discontinued by the manufacture and is no longer available to purchase. You can use Item#s2362-1933 [https://www.thebroadcastshop.com/Store/17861] as a similar substitute with the following caveats: You will only be able to secure the rosette with 2 screws (instead of 4 screws) and will not be able to secure the rosette with any pins.
#1800-60 (sko13e0460) Attaches To Head With Qty-4 #M4x12D7991A2 Screws And Qty-2 #4M6x10D6325 Pins