If you can safely tow your trailer using the CIPA mirrors and save some money, why not?
At one point in time the CIPA mirrors were available at Walmart (not sure if they still are).
If so, get a pair mount them on your 4Runner, hook it up to your trailer and see how they work for you.
When testing out these or any mirrors be sure to take the trailer out for a test tow on the roads and highways.
See how the mirrors perform at highway speeds. Do they seem secure at high speeds?
Do they make excessive wind noise that will annoy you on a long trip?
Do they stay where you put them or move around some due to wind resistance and vibration?
Do they provide an adequate view whendriving, parking or backing up your trailer?
Good Luck with your search.