LA Theater Works, producers of The Play's The Thing, the public radio series of plays read for a live audience by famous actors of stage and screen,
sells dozens of their recordings on CD. Search by title, playwright or actor. Seems priced for a library or avid collector, but it's the only official way to get quality recordings.

A less official way to get recordings is to set up your Mac with Audio Hijack to record the live broadcasts off the Internet stream of an appropriate public radio station. (Alas, my laptop is my main computer, and I don't leave it on all the time.)