I searched the forum, and found a few threads on towing mirrors, and have decided to try my own solution.
Today I ordered these from Mr. Bezos.
My hope is to do the following:
1) drill a hole somewhere on or near the bottom outside corner of the existing mirrors.
2) Insert the rivet, nut.
3) Use the correct size screw to tighten down the rivet nut, thereby expanding the rivet, making it a permanent mount
4) Use a wrench to screw attach and adjust the convex mirrors that I purchased.
If all goes well, maybe I'll have some decent towing mirrors that I can quickly put on or take off with one wrench.
I'm probably going to put a backing plate on the inside of the plastic of my existing mirror, to reinforce and spread the load from the grommet.
I'll probably use a stainless steel fender washer. If I find a thin piece of some type of rubber, I might put that under the washer, to allow for some padding and to provide a little give and dampening effect to help make the mount more secure.
Lastly, If I seems a little weak, maybe I'd put some epoxy over the inside, or make a "cavasil" paste from epoxy and use it to reinforce the area.
Those are my plans. I'm not sure when i'll get to the project, but I'll post back on my results.
My hope is that by putting the nutwell on the bottom, it will be fairly innocuous when the mirror is removed, yet allow for a simple, secure and clean mounting when the mirror is installed.
I looked at some mirrors designed for jeeps that mount via a bracket with two holes per mirror. While that seemed like it could be more secure... to have a bracket and two screws holding on each mirror, this solution seems simpler, has a convex mirror and was less expensive, so I figured I'd give it a try.
:-)
---
P.S. -- My plans were inspired from looking at and extending other options.
For those interested in towing mirrors, I've seen the "dumbo" mirrors from a Tacoma that one member put on his 4Runner, with a little modification and help from a heat gun for the trim.
I've read that some of the Dodge mirrors can be fit on a 4th gen... with a little modification.
I've read that some have had luck putting tundra mirrors on their 4th gen again with some modification.
The consensus seems to be that strap on mirrors are less than satisfying.
Mirrors that slip over the factory ones don't fit the 4runner.
Some people like ones that mount on the door using hinges and straps. Some people don't. It seems that you need to be careful on installation so that you don't damage your paint or crack the plastic lower body cladding.
There is a mirror that mounts with a suction cup, and has a short leash in case it falls off.
Those have had mixed reviews. Some people like 'em. Some hate 'em. It seems that it can be OK if you don't overtighten the handle for the suction cup. There isn't a built in stop, so if you overtighten the suction cup, you will strip the gears and then you'll be unhappy.
Some people like these. Some have complained that the mirror fell off, and then the mirror banged up their door as it was hanging by the safety leash.
I liked the posting by one user who said he drilled hole in the upper corner of his mirror and used it to mount a 3 inch (i think) convex mirror.
Putting all of these ideas together, and having owned a motor cycle (sport bike) in the past, I started thinking, maybe I can add some type of insert that stays on the mirror and allows me to screw in a convex mirror.... preferably near the bottom outside of the mirror, so that it's less noticeable when the mirror is removed.
Thanks to all of the other forum members for sharing your work, experiences and ideas.
We'll see if my plans work out well or if they just seemed like a good idea.
Thoughts, ideas, suggestions and feedback are welcome... both before, during and after my work!
Oh! I just realized that have some dynamat copy cat material laying around. it is butyl rubber attached to thick aluminum foil and designed to be used as a sound dampener. Maybe I'll put a small piece inside the mirror where I plan to drill the hole, then put a fender washer over it... also on the inside to both reinforce and provide dampening for the well nut and to spread and relieve pressure from the mirror when it's mounted.
Thoughts and Improvements on the idea are welcome!