General garage door parts like rollers, drums, openers, remotes and other items can be purchased on the manufacturer’s website. Also, you can purchase the parts on distributor’s websites like hardware stores and Amazon. Some parts are carried in your local hardware store.
Before you purchase a part for your door, consult your owners manual for the part number. If you are missing the manual, look on your door for the model number. Generally a sticker is placed in either the lower right hand or left hand corner of the door with the number.
If you need to replace a part on your opener, you will look at the opener for a model number. Sometimes it can be found under the light cover. Other times it can be located on the side of the opener.
After you get the serial number and manufacturer, you can look for parts that are compatible with that model.