It seems that the best place for a person to purchase pocket door hardware would be a hardware store, or a chain home improvement store like Home Depot, Menards, or Lowes.
Cheap door trims can be purchased at most home improvement and hardware stores. Sears Hardware, Home Depot, and Lowe's all sell cheap door trims in their stores.
Garage door parts can usually be found in stock at Lowes hardware store for virtually any type of door. Even if your local Lowes does not have them in stock, they are able to order them for you and call you when the parts arrive.
Schlage door knobs can be purchased at most major hardware retailers. Examples are Lowes, and Home Depot. But some smaller hardware stores will carry them as well.
You can purchase a cheap commercial door directly from the manufacturer. You can also try larger home goods stores and hardware stores, such as Ace stores.
One can purchase bulk door levers from hardware stores, specialty door hardware retailers, or online websites that specialize in bulk hardware orders. It's recommended to compare prices and quality from various sources before making a purchase.
Door stops can be purchased at any hardware store such as Home Depot and Lowes. You can also find them at many discount department stores like Walmart.
Canadian Tire and Home Depot definitely have a good selection of sliding door locks. You may also want to try Lowes, Costco, Walmart or Home Hardware.
Home Depot, Lowes or any hardware store
One could purchase Baldwin door hardware from Lowe's if one lives in Chicago. There are also online websites such as Build and Door Hardware which also sell Baldwin door hardware.
Door alarms are available at most home improvement stores such as Home Dept, Ace Hardware, and Lowes. Stores specializing in home security will also offer door alarms for purchase as well as offer installation services.
Many of your local hardware stores carry replacement glasses for fireplace doors. Stores like Lowes and Home Depot are great hardware stores that carry these items. They also carry the glass door themselves in which could be cheaper then just replacing the glass.