There are a number of ways in which you can find gas furnace parts from burners and gas valves to other parts that you may need for a furnace. You will need to narrow down what you need when looking for the parts because there will be a lot of searching involved in finding the items.
Step 1. List the Parts
Begin by using a notepad and writing down the parts that you need for the gas furnace from the most important to the least so you will have a hierarchy in knowing what is most important to find when searching. You will also need to find a serial or service number that will be located depending on your unit. Some have them are hidden behind other objects like a metal cover or a access door. Check your manual or with your manufacture if you have problems locating your number so you can use it later on if someone asks what type of a furnace that you have.
Step 2. Try the Manufacturer's Store
The first shop you should try to find is your manufacturer of the gas furnace. When you find the shop, you can ask them if they have any parts that you need for your old furnace and if they do not you can ask if there is any other parts that you can use as a substitute for the part.
Step 3. Hardware Stores
Another place to try and find parts for a gas furnace is any type of a hardware store as these will have a wide range of parts and tools that you might find at the store. You can check the aisles for furnace or heaters and see if there is a part that could work the same if it is newer. Also ask the employees at the shop for any help in finding parts you need.
Step 4. Other Stores to Try
In your area you will also want to visit a recycling warehouse or shop that sells old parts from computers to furnaces. As these could have a part that you are looking for.
Step 5. Searching the Internet
Having access to the Internet can give you more success in finding what you need than only relying on retail stores, although this can take longer because you will be searching for the part that you need which will take time.
The first step in finding your part is by using a search engine of your choice and type in the part that you need with the word buy into the search box field. This will come up with a wide range of places that you can click on for more information on the part that you need.
There are other well known sites like Ebay which sells a wide range of products and old parts that you can type into their search box and see if your part comes up to bid on.
Also, craigslist can be a very good site in which you may find an old part to a furnace by looking under for sale and under the categories of free in which you could find another old furnace in which you can salvage the parts and use those. Also, on craigslist you can make a post and ask if anyone in your town has old gas furnace parts.
With the list of places to go to you should have a good chance in finding the parts you need.