You can usually find replacement brake pads by searching for the model of brakes installed on your bike. Make sure the pads are the same shape as the ones you are replacing, if not, that is a good sign that they are not compatible. If you are not sure, it may be best to visit your local bike shop!
Our bikes that use disc brakes all use the same type of pad which are Tektro E10.11 disc brake pads. There are different pad compounds that can be purchased depending on your climate and riding style.
You can purchase replacement brake rotors via Amazon or your local bike shop.
Be certain to match the size listed below for your bike.
Core 5/ 500 Series: Tektro Aries 160mm rotor with 6 bolts.
700 Series: Shimano BL-MT200 180mm rotor with 6 bolts.
Tektro HD-E350 180mm rotor with 6 bolts.
LMT'd: Tektro Auriga Dual Piston Hydraulic 180mm rotor with 6 bolts.
This video from Parktool explains it very well and may be more than you ever needed to know about brake pads!
It will show you how to replace them and discuss the different materials available.