That was one of my FAV. radio shows as a child! I even ate shredded whet to collect the Sgt. Preston cards. ;^)
Is the LibriVox app available on your internet device? If so, you might want to download it (it’s free).
LibriVox has hundreds of “Challenge of the Yukon” episodes. Plus audio files on other old-time radio shows. I listen to them when I can’t sleep. Plus they have audio files on a million other topics.
Everything is free and legal to listen to - and download if you wish. Legal, because everything on the app is in the public domain.
Theres only one down-side. There are no “Challenge of the Yukon” episodes in Hungarian.
😀