Those are the only ones I need to finish all quests in the game. --- For those who want to do all of Xenoblade's sidequests, I pray for you sanity....... http://www.twitch.tv/kyokusanagi92, Ye olde stream.
They're a pain (I had a thread about them a few days ago).
I suggest you try exploring these areas in order : Tolbaran road, Sogd road, Seirai road and Katamarca road. Then save, title screen, reload and repeat (you can skip any of those areas after you've gotten the Bacura that spawns there)
Sorry for second post. Just for kicks, found normal Bacura in the second area of Tolbaran Highway. Bronze Bacura can be found in Zog'd Swamp. Coming from Ni' Akeria, it's the second area after you climb up the cliff.