I started with these - they were "ok" but had a lot of vibration. I did not care for them: http://www.google.com/products/catalog?q=rv+mirrors&hl=en&cid=17001946602065581576&ei=GCI7TOGLFZW6wAWv9s2ODg&sa=title&ved=0CDsQ8wIwCTgA#p
Then, I went to these which are much better - I would recommend them: http://www.amazon.com/CIPA-11900-Custom-Towing-Mirrors/dp/B000CISLUG
(I did not use these specific retailers - these are just the links I found today. The 1st mirrors came from Wal-Mart and the 2nd ones from Camping World.)
There are also extendable mirrors (both manual and electric) you can buy that totally replace the factory mirrors already on the truck but they can get quite expensive.
I also stuck a small round convex mirror on each truck mirror and find them helpful (even without the trailer in tow).