Looking For Block Circuits

I was watching videos about AM and FM on YouTube. I saw a video and can't find it now. In that video was a block diagram-like circuit. It was a physical, actual block circuit. All the blocks like LPF, VCO,BPF etc were built in little metal boxes and these boxes were connected to each other with a coaxial cable and all this system was fixed on a board (it looked like coaxial i dont know what kind of transmission line was used actually)

The circuit blocks (metal boxes with white labels on them) were sale on the website in the description box of the video.

I really need any kind of ready to use blocks. Have anyone of you seen that video? Or can anyone enlighten me about if that kind of circuit blocks are sold?

Tank you all