Most scholars seem to believe that kava was never very popular in PNG. It's actually very hard to grow it there (at least according to the Pacific Elixir) and they have seemingly only managed to cultivate the more resistant cultivars. From what I understand, none of the cultivars present in PNG is noble.
We used to sell a great PNG we called Koniak. It had a not so noble chemotype but didn't produce negative side effects often. Unfortunately we just can't get it anymore. It's simply not much of a cash crop there. As @kastom_lif mentioned, if you can find a Hawaiian Isa the effects would be similar to a non noble PNG cultivar. Whether you will like it or not, who knows? I've found some Hawaiian Isas to be pretty pleasant and despite not being noble, relatively mild.
Isa is from PNG. Not to many people grow or sell it here in Hawaii anymore. The kava bars tell me that there customers prefer Hawaiian kava and they did tell me that very few did not mind the Isa but most did not like it, they actually would ask if the kava was Hawaiian or if it was Isa, if it were Isa then they would pass.
I did a review of all the kava bars in Hawaii for my presentation for the 2015 International Kava Conference and this is some of the information I got from them.
Aloha.