No such cable exists.
The ACD PSU uses a proprietary Apple connector. Nobody has ever made an extension for it. Gefen had an ACD combo cable that cost around $220-$300 once, but that has been discontinued and it didn't extend the power cable.
Your only solution is to extend all three cables (DVI, USB, and FW) separately, and hang the PSU off where you make that connection, then use a longer power cord. If you use cable binding to tie it all together, this can be a clean solution, even though you'll have to deal with the white brick in the middle of the extended chain.
-SC