For the AC inlet, when I built mine, I simply gutted a bad PC Power Supply and took that part, but I also found them in the Digi-Key catalog. The key to finding them was looking under 'Power Entry Modules' and going to that catalog page, and then you found a slew of them (both fused and non-fused, so you may find the fused one more useful unless you already have an external fuse holder).
I never did find a red/green/blue knob, but later ran across someone mentioning mouser as the source for those unless my memory has failed me.
I've never seen the plastic DB-15 hoods.
-Dan