There is no quick way to earn this achievement. It will come in time.
You can increase the chance of Eternity Splinters dropping by stacking Special Item Find (SIF). However, it may be a better idea to focus on stats as the following equation applies:
Max DPS = Faster Kills = More Loot = Increased Chance of Drop
You can find SIF in the following places:
- Item Stats
- Deadpool has a lvl 50 synergy bonus to +10% SIF
- Costume Cores
- Runeword: Brigand's Fortune