Awesome pic, TridCloudWalker.
bigcow, a hollow Obi ROTS will be hard to find. I haven't seen one (film accurate) anywhere, actually. There are the MR FX hilts which can fit soundcards, but obviously they are far from proportionally accurate. If you do find one, let me know!
The other concession to consider is that a saber with a soundcard implies that you are going to want a blade attached, and in the case of the Obi ROTS (or any of the similar grenade sabers for that matter), the neck and emitter are too thin to accept the LED, optics, and deep enough duelable blade holder while still remaining film accurate.
There was a sabersmith on FX-Sabers with a converted Parks Obi ANH with a 3/4" blade, but I can't recall if it had a soundcard in it yet...
'Not to say a close facsimile could be made (modified TCSS MHS or an extended emitter), but it wouldn't approach the accuracy of, say, the scale/proportions of TridCloudWalker's saber he posted.
Good luck on your search..