Ah - good that you are communicating with him.
I see Hank has tapes and audio CDs of Jan Garber material, but didn't know if he made the step to MP3s. If not, there are several shareware and commercial programs that will "rip" an audio CD, to make MP3s. One could purchase audio CDs and make one's own MP3s.
One problem is the large number of audio CDs that are needed to fill a CD with MP3s. Some folks don't want to spend time ripping and making quality MP3s.
Another problem is that new OTR MP3s soon appear on USENET boards that cater to fans. That means one person could buy a few audio CDs, make MP3s, and distribute them as freebies to the vast audience on USENET. Although "good" for the fans, it is "bad" for the original sellers, since they would then sell much fewer audio CDs of the material.
As yet (as you have noted), there are few to no Jan Garber recordings floating around the net. Even http://www.mp3.com/albums/106542/summary.html
doesn't have any downloads available.
Some folks have considered a compromise ... sort of like the old OTR clubs, in which club members copied and shared open-reel material among themselves, but not with outsiders. Perhaps one of those club members might read your post.