Hi,
I dug out my order, it was back in 2012.
US Spars, Inc.
6320 NW 123rd Pl.
Gainesville, FL 32653
The part number is: 1618 the description is: Sheave 60x16x8 Delrin. There are four on top of the mast.
(Aft: main halyard, topping lift. Forward: Jib Halyard 1, Jib Halyard 2 (neither of which is used as I have a CDI furler).
You can see the 2018 parts catalog online, and the sheaves page is shown below.......
I don't have a spinnaker, though I do have a spinnaker bail to attach a block to. You can just see the spin bail at the top edge of the picture.