I would suggest just playing through the game normally on your first run, saving this trophy for a second playthrough or later. The best places for this would be XP Shell (where you only have Antibodies) or trying your luck with Moebius Factory for the ? Leader creatures (Pom Leader, Wolf Leader, Roc Leader, and I think there's one more but I never saw it) as they give a lot more than the Antibodies themselves. You can also use this to grind out a lot of DP doing this.
*NOTE: Apparently, using a Stress Doll as an accessory increases your experience value, so by the time you have access to XP Shell, you should have at least three normally to equip.