Let the hive mind of Engadget get that for you.
"I commonly need to boot a system from an external disc and take a snapshot of the host system. I also then need to burn a copy of the image to a DVD. While I can do it with two separate external devices, and two power supplies, and two I/O cables, it'd be nice to find a small dual-drive enclosure. It would need to have USB, eSATA, and FireWire. Either slim-line or half-height bay for the optical burner would be fine, and space for either a 2.5- or 3.5-inch hard disc. Any ideas?"
https://swdlp.apple.com/cgi-bin/WebObjects/SoftwareDownloadApp.woa/wa/getProductData?localang=en_us&grp_code=itunes&returnURL=http://www.apple.com/itunes/download&isMiniiFrameReq=N