Power button is broke. Where do i get another

Solution
Might not be the power button.
But if it is:
Disassemble the laptop case around the power button. If the button is on a small board with some LED lights a cable then it is usually possible to get one for cheap on eBay. If it's on the main board then you'll have to desolder it and solder on a replacement (they are usually commodity items available from an electronic parts supplier).
A few bits of information about your laptop (name and model number) would be helpful, but you could try:
1. Contacting the laptop manufacturer, or
2. Search eBay or Amazon.

Depending on your laptop brand power buttons can usually be replaced, but in some cases (Apple products) it's going to be next to impossible if not actively discouraged.
 
Might not be the power button.
But if it is:
Disassemble the laptop case around the power button. If the button is on a small board with some LED lights a cable then it is usually possible to get one for cheap on eBay. If it's on the main board then you'll have to desolder it and solder on a replacement (they are usually commodity items available from an electronic parts supplier).
 
Solution
you don't sound like one who is experienced with such repairs, so i recommend that you either try to contact the manufacturer , or drop your laptop to a local repair shop!