I'm in Act and I'm getting mats for Talisman quest. I have everything but the freaking Endraga fetus. I have killed over 100 of those things and nothing has dropped. Checked all the vendors and no dice. I feel like kicking myself for not realizing that it could be used in crafting. Also I have exhausted all the cocoons.

I am fairly sure i got all mine from the cocoons. There is a Mod that makes these things available if you want to try that. Other wise, perhaps go back a save or two and try to gather a few-- not sure how far back that would be for you at this point?

doesnt help that they are called endrega embryo in game ;)