Somehow I managed to upload the wrong video previously and never noticed. Here's the correct part 4.... Got construction of the twist wrist done, working now on the hydraulics on the excavator. So close to having it finished!
I got this particular valve from Princess Auto. It's a Rexroth Bosch L721C116AIOB010, if I got the numbers right. Generically these are called a 6-way 2 position selector valve and they're fairly common and available through most hydraulic supply chains.