Hp power cord extensa

My laptop power cord is not working. where can i buy one ? laptop details are acer->extensa 3650 z. New or refurbished one will be ok for me.
 
I assume you mean the external power supply and battery charger, commonly known as a "brick"?

Three possibilities:
1. Contact an Acer dealer for a replacement.
2. Something like eBay.
3. You can find "universal" power supplies with switchable output voltage and power tips in many electronics, computer, and stationery stores that sell computer accessories.