I don't know if you've found anything yet, but I thought I'd throw my $.02 in.
Phonak makes a device that will broadcast a signal from any music device directly to your "hearing instrument" (as they call it). I don't know that it's compatible with your 'aid, but since it's a Phonak, I think it might be worth looking into.
It also works as a remote for digital 'aids, a bluetooth device for cellphones (the cell will broadcast directly into your hearing aid), an assistive listening device, and a few other neat things as well!
http://www.phonak.com/consumer/produ.../smartlink.htm
If that doesn't offer the ability to create mono sound, you could probably use that with a mono converter and not only have sound in only one ear, but it'd most likely be QUITE comfortable, since there would be no external "stuff" to wear...it'd just pipe it through a speaker you're already used to (your aid). I'd imagine the sound quality'd be excellent, as well, considering that a hearing aid is probably going to be much higher quality sound than a headphone playing into a hearing aid.