Portable pen on wheels, looking for DIY design 'cuz I'm in Ecuador!

My husband and I are trying to get a portable pen built, with wheels, as seen in your video. If there is any chance you could share with me any information you (anyone?) still have about that design, that would be helpful.
For instance, is PVC sufficiently sturdy or was the one in the video aluminum or another material? It's not clear how the wheels are attached, is there any insight you can offer about that?
The plans I was hoping to get from the forum are not exactly what we had in mind, at least what I've been exposed to: I may need to be guided in the right direction if they are here somewhere.
Thanks in advance!