Energy Cells
Small, non-rechargeable "super-batteries", used to power plasma rifles, H.U.L.C. armor and other high-tech gear. Using technology (nuclear fission or antimatter?) beyond the capabilities of modern Ikaanos, humans on Raana rely for these on the old Earth stock that's frequently delivered from the Mastersphere to various certified vendors on Emerald Island.
Not readily available in shops, you can find them occasionally while scavenging (assign staff to the Scavenger role if you want a steady supply) - they sell for $50-$100 depending on economic conditions in Ikaanos, or you can keep them to use.