For the type of fertilizer you described, you can try something like bone meal, manure, or even coffee grounds.
assitant
What materials do you have available to you?  This is going to be a bit of a custom answer, but I would use something like bat poop.
assistant
How can I make my own fertilizer?
user
What is your goal?  There are many different types of fertilizers.
assistant
I want my plants to grow well.
user
It sounds like you want a fertilizer that gives the plant extra nutrients, like nitrogen, phosphorus, potassium, and iron.  Did you have a specific type of plant in mind?
assistant
How do I make that?
user