The blue black connectors can be easly found on ebay or other similar places under pneumatic push fit connectors. They are cheap and easy to use. But only go to 10 bar. I have used many in my robots as i had to keep the weight down. But best to use them as a prototype then change to stronger metal fittings when you proved the setup works. I have had so many plastic ones break in fights due to cold, pressure and impact shocks. Not reliable. Remember JAR in robotwars Christmas special had same issue.