I got my 3/4 to 5/8 from Tractor Supply Store they come in nylon and work great for me no leaks just add some pipe dope .
I just finished making mine, and lets just say it was a NIGHTMARE. Everything possible went wrong for me. I had leaks everywhere I ended up taking it apart 3 different times. Also this reactor is WAY more expensive then the R.G style I spent around 20 or so on it and I believe im over 60 on this Cerge reactor. Mainly because I could only find 3/4 to 5/8 brass barbed connectors. Yeah it looks nicer but I'm not sure if it was worth the head ache.
I ended up gluing some parts. Right now I have the co2 turned up more then it was with RG style reactor and getting a darker green drop checker... Kinda frustrating. I was thinking of taking pictures but forgot in my rush to instal it, then after fighting leaks it slipped my mind again.
I followed the design of page 10 using the same housing on page 1 but with a clear bottom.