Project: inspect boom, sand and paint, replace lines and boom sheaves as necessary

As mentioned in an earlier APS has a 20% sale going on at this moment

Discovery is a 1983 Ericson 30+ with a Kenyon 003315 boom (look for information at goose neck)
all sheaves were in good shape except two small 1" x 1/2" plastic sheaves

Google search for replacement parts: Kenyon Boom 003315 goose neck replacement parts
Reefing Sheave for 3756 Gooseneck: K-11412:
Delrin sheave is 1" OD x 1/2" wide x 1/2" ID.

Cost: $57 each

WHAT The ?

Anyone have a less expensive source for this LITTLE sheave?