A look at what is currently available on eBay

Two 2 Channel 5V Relay Module Expansion Board For Arduino ARM PIC AVR MCU DSP
US $4.39

DPT SX4055U2 DPT Two Channel SCSI Bus Expansion Module
US $210.00

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DPT SX4055U2 DPT Two Channel SCSI Bus Expansion Module, Two 2 Channel 5V Relay Module [...]