There's many old videos on media.ccc.de with very low quality, standard definition camcorder and without slide capture or at maximum grainy vga captured slides. Might it be possible to take re-render those to FHD or even 4K with everything upscaled and the projector replaced? Would need some additional magic to recognize laser pointers, mouse pointers and the presenter walking in front of the screen, but might be worth it for some of the more timeless talks.