Your first chance to get this trophy is in Neptune’s Bounty. The Gatherer’s Garden is on the upper floor after you pass through the Lower Wharf (can’t really miss it as you are gonna pass right by it following your quest arrow). A Plasmid Slot will be the first thing on your list when you choose to purchase something from the Gatherer’s Garden. It will cost 100 Adam so if you have enough, select it and the trophy will pop.