For this and all other achievements, I strongly recommend following MaGtRo's excellent guide: http://www.gameboomers.com/wtcheats/pcTt/TBOUT2/TBOUT2.htm
It was not written for the Xbox, so it doesn't reference achievements ... and doesn't talk about "trophies", either ... so not a PS write-up. Regardless, it gets you through in a reasonable manner.
And, for this part of the story, having a guide is really handy as the game takes you from one land to another for infinitesimally small details and pick-ups. Frustrating. At this point, any magic the game had is lost in a sea of mindlessly running from one land to the next. And back again.