We don't have a Ridgeline, but we use the same mirror as dhinkle57. They're available on Amazon for $30.93.
We also mounted the 5 inch convex mirror to the bottom ($8.87 each).
Amazon.com: CIPA 48500, 5" Round Convex Black
They both work perfectly so far (we've only brought the new TT home, about a 70 mile trip). Once you set them up and adjust the mirrors (be sure to loosen the screws to adjust, then snug them back up once mirror is adjusted), then you just re-install for next use and your good to go. Just my .02 cents. Good luck and happy camping!