I can't find him anywhere in bioscience. Apparently he gives you a mission called Building a better crop but I never did it.. Where else can I find him? I just did the house divided mission which involves Issac. Ah man, am I too late at this point or can I still find Issac and get the mission called building a better crop?

Are you on PC or console? If you are on the PC, then you can use console commands to teleport your character to his position. You might have to wait a few hours after leaving Bioscience for him to show up or he is taking a break.

Just did that quest, and I've done pretty much everything else.

He may be somewhere else, wait a while, come back...