Diplo drops from Ultimate Tyranno Hassleberry, not the regular one.
I still need 1 more, so that I don't have to get the one in EX Card Trader, as it's crazy expensive.....the EX jewels are better spent for the booster gems.
It's not like Konami giving boosters out almost every event or campaign they are even more rare than let's say a lousy card like toon kingdom so definetly get those boosters boi
1st copy: Event reward.
2nd copy: 300 EX Jewels (Hassleberry Event) in the White Card Trader.
3rd copy or more: random reward from Ultimate Tyranno when defeating him.