Most new portables have this capability. Just look for one that says it will play MP3 CDs. Then you can just burn the MP3s to a disc and play them, the advantage being you can fit about 6-10 CDs worth on one disc.
And, does he just download the mp3s off of the net? I'm aware there's cost involved now. (well to do it legally, right?)
Right. I haven't really tried any of the new commercial sites yet, but I think the leading one is Apple's iTunes. Another option is to copy CDs he already has into MP3s. I always loved being able to take discs of MP3's to work and have a wide selection of my albums available on only a handful of discs.