You NEED source code? Write it yourself!
Start with requirement gathering. Think, think, and think what should that system do. Write them down one by one in a sheet of paper.
And when you have figured out what it should do, try to implement them one by one. (And if you face problems in this phase, you're welcome to ask anything here. Nobody will give you the "source code for attendance management system")
And just as
OriginalGrif has said, you may find it easier than you think.