Does anyone know the part number for PCB mounted Costar or Cherry stabilizers?
There is no such thing as "PCB Mounted" Costar stabilizers. All Costar stabilizers attach to the plate.
Cherry "Plate Mounted" stabilizers are parts: G99-0224 (1x2, 1x2.25, 1x2.75), G99-0379 (1x7), and G99-0226 (1x8, 1x9, 1x10).
These Cherry part numbers are "without frame," and I'm not sure if that means "PCB Mounted" or what: G99-0742 (1x2, 1x2.25, 1x2.75), G99-0745 (1x7), and G99-0744 (1x8, 1x9, 1x10).
This is the link from Cherry:
http://www.cherrycorp.com/english/switches/key/mx.htm