There is a seller on eBay with a bunch of used rip fence extrusions for sale. As you may know this is the same extrusion (clever, Ryobi) as used in the miter fence, but longer.

If you want to upgrade your miter fence from 14" to 23" for better support of miter cuts, here's an opportunity for $19 shipped cost. I'm sure he has a limited stock of them.

I ordered one, coming on the 21st.