Ordered one of these (Syba Best Connectivity 2.5" IDE 44-pin to Dual Compact Flash Adapter) and verified it works great for the empeg. Plugged both cards in, attached the cable, and it just worked. The form factor is also perfect for mounting directly onto the hard drive carrier with no modifications needed.

The adaptor doesn't do anything special to try and combine the two flash cards into one virtual drive though, so this isn't a solution to add 4 CF cards to a Mark 2 unit. With the Mark 1, this would be a great way to go though cheaply.