Maragret, Luigi Falcone sells them in Teverola. If you exit the base and keep right onto ss7 (don't go over the bridge) take the first exit, follow the sign at the round a bout to the Medi Mall (3rd exit I think) once you have taken the exit follow the road to the end, 2 choices right goes to the Medi Mall and Savaris, left goes to Luigi Falcone. Take the left and go under the bridge, Luigi will be on your left approx 1 to 1.5 miles. He does have the colored Demi Johns (blue, red, amber, purple, yellow) and will tell you these are natural glass not painted, they are priced up to 20 euro more than the clear or green ones depending on size but they are unfortunately painted (I am talking from experience)
If my memory is correct for clear and green
5 litre = 5 euro
10 litre = 8 euro
the giant one was 18 euro, and all the other sizes are in between that ;0) there is a price list on the wall as you walk in the yard. He usually has them outside
The other Luigi that many do business with has a shop in Lago Patria, I will see if I can get directions to that. His stands, candle holders are much nicer than Luigi Falcones and cheaper.