You can download the schematic for the I/O Multiplexer and the BOM from this page.
I have also created an online BOM on Mouser.com that you can use to order all of the parts required to complete the I/O Multiplexer PCB kit with just a couple of clicks.
Schematic
Bill of Material
You can purchase the materials needed to complete the PCB kit from Mouser using this link or you can download the BOM Excel file below and order the material from the vendor of your choice.