Many (all?) episodese were released by PBS on VHS:
http://www.amazon.com/s/?_encoding=U...as%3Dmovies-tv
Granted, the tapes cost a few dollars, but they were $25-20 per volume from PBS all those years ago. You can grab them now for $5-10 each.
The original tapes probably look MUCH better than typical Youtube butchered encodes, too!