Hi Suzi,
Awning rails are a stock item at most RV shops. They come in 2 sizes so get the one to match your
awning. They also come in different colours (aluminum and white).
Some people are attaching them with VHB tape rather than rivets. Search here for awnings and tracks before making a decision. The 4' are meant to easily ship, the 8' is standard, they come longer.
Somewhere here there is a thread that shows pictures of various awning lengths, brands and tracks on our trailers. Sorry I don't have any time left this morning to search for you.