Tips on searching for Lost Media?

I've been trying to find information on the Wolfman Zapp showtapes for about a year or so. I've done almost everything I can think of to try and find anything that could help, I've looked through old commercial compilations, I've looked through old newspaper archives, I've tried contacting the creators, and it's just been dead end after dead end. The most noteworthy thing I've found is finding some old addresses of the locations. So for a while I've just kind of been checking in every now and then and seeing if anything just happens to show up.

So, with that I ask, any tips for searching for Lost Media? Is there anything else I can do to try and uncover stuff, or should I just keep sitting and hoping something happens, lol