Check out at the bottom of this comment for update - Believe it or not, there is a high likelihood that out in my garage on a regular reel to reel audio tape is the sound track recording that I recorded that night in 1968 from the TV show. No video, but the audio was complete with no surrounding room sounds because I recorded it direct. Long ago my reel to reel recorder failed me and I never got a replacement since they seemed to fall out of favor. I'm computer savvy though and sometimes entertain thoughts of finding one to convert it to mp3 or something. If that ever happens I guess I could make it available if legal to do so. Great production.
I found the reel to reel recording but have not managed to digitize it yet - I got ahold of an Akai M7 recorder but am having trouble transferring the play/video/tv production to my laptop and from there to flash drive or DVD etc.
I have now digitized it in RAW form - gotta use some filters on it but it sounds pretty good. Thought of offering it to George Segal and Nicol Williamson's kids and any one else in the production or their kids (wouldn't be kids anymore though, would they?) Any one know how to contact them? WAV file is 1.25 GB so not big.
Just after I did the above, this version of "Of Mice and Men" became available from places like Amazon etc. On DVD!!!!! The full video including the 1968 commercials.