If you look at the parts list in the "Cheap & Easy 10 Gallon Rubbermaid MLT Conversion" thread linked a few posts up, you'll see that the part that's the connector on the inside of the MLT in FlyGuy's design is a 3/8” male barb adapter (Watts A-294). Pic below (borrowed from FlyGuy's thread):
The plastic fitting you see on the inside wall of my MLT...
...is a CPVC female 3/8" threaded to 1/2" CPVC female socket end fitting. It screws on to the brass ball valve fitting and the horizontal CPVC coming off the manifold just pushes into it. It replaces the 3/8" male barb adapter in FlyGuy's design. Other than that, I followed FlyGuy's design as posted.
So to build a manifold like the one I did, you need:
(8) 1/2" CPVC 45 degree elbows
(3) 1/2" CPVC tees
(1) 3/8" CPVC FIP ADAPTER (female 3/8" threaded to female 1/2" socket end)
(1) 1/2" CPVC 90 degree elbow
(1) 1/2" CPVC 90 degree "street elbow" (same as the other 90 elbow but one end fits *inside* the center tee)
(1) 5-foot length of 1/2" CPVC pipe (a 10-footer costs about 70 cents more...worth it in case you need practice)