Have to check Orient photo and mabbie the other studio suppliers in the mass order section. The studio outfitters may have something that works. Honestly I not sure as I never use portable battery. But in general, going by the prices of the China made portable flash kits, if one is available, a separate battery pack probably won't cost more than a few hundred?
What I just found in a quick check is that there already are battery packs that can be used...
[vid]jsxktBqKBu8[/vid]
Also some discussions below the video: http://www.youtube.com/watch?v=jsxktBqKBu8
http://www.white-lightning.com/VIIsystem.html
And according to this discussion, any inverter pure sinewave battery pack should be able to work:
http://www.fredmiranda.com/forum/topic/814402
Interesting discussion by folks who already tried battery packs with the Dlite 4s: http://photography-on-the.net/forum/showthread.php?t=805119&highlight=battery+pack+for+Dlite
More discussions: http://photography-on-the.net/forum/showthread.php?t=688912&highlight=battery+pack+for+Dlite
This was also mentioned in other discussions: http://www.innovatronix.com/detailpage.asp?productid=363&categoryid=42
And someone who DIYed a battery 'pack' for his Dlite: http://photography-on-the.net/forum/showthread.php?t=689719
