I have struggled with this problem for years. Custom solutions cost a young fortune, on top of the 2K per ear cost of current technology in the hearing aids themselves. I like to wear wireless headphones to listed to TV, especially while I am cooking. My hearing loss is pretty symmetrical, so I can either get headphones with a good range of volume and wear them without my aids (only viable at home), or look for headphones with deep cups that will fit over the aids. That only works for a while--even the biggest cups eventually get uncomfortable because they are jamming that hard plastic into my skull.
For my mp3, I use over the ear clips. It's not a good solution because not only do they look funny, the sound is not actually picked up much by my over-the-ear aids, so I have to have the mp3 at pretty much maximum volume. Even the maximum is barely enough with some sources. Also, between the hearing aids and my eyeglass frames (don't suggest contacts--they don't work with my vision), I end up with a lot of stuff behind my ears and the clips fall off a lot. They also tend to pull my hearing aids out from behind the ears when I take them off. They are, however, the only style I have found that doesn't do the jam-the-aids-into-the-head trick.
A super cheap solution for TV and other ambient sounds is to use one of those battery powered amplifiers you see advertised on TV. You can use the ear clips for comfort and the sound volume is good, but a $20 amplifier is going to sound tinny at best. Also,they amplify everything, not just the signal you want to hear. They don't work with mp3's, afaik.
CNET folks, this is one problem that would be an EXCELLENT project for your professional reviewers. Surely your staff includes someone (or someone with parents or grandparents) with hearing problems who would love to test headphones and provide specific information for the growing number of people with this problem.