How do I go about finding the monsters that drops the materialsfor the..

Before you start searching, you want to make sure you are very high leveled. For the first replica monado (rudra) you are going to wanna be at least level 78, no lower because if your enemy has a red portrait, almost all of your attacks will miss. If it's yellow, you should be fine. The enemies you are searching for for this monado are: Green Feris, Royal Caterpile and Magnus Ardun. The green feris can be found in Satorl Marsh, near the silent obelisk, and you collect the lucky fang. The Royal caterpile can be found in the windy cave on the bionis leg and you collect the caterpile silk. The magnus ardun can be found at Rho oasis on the bionis leg, and you collect the ardun elder beard. The green feris is the highest level monster, it's lowest level being 83. So for this quest you want to be level 78 at least.