They all get sloppy where they won't stay in place where you put it. and after driving the wind will move it ever so slightly, but enough on a Class C that you can't see what you want to see.
Mine was the passengers side where I couldn't safely move over on many occasions. :R
I bought a piece of clear tubing they use for fish tank water air pumps. Cut it fold it and stuff it in you can't see it and the mirror hasn't moved since.
Sounds like you are describing a Velvac swinging-arm mirror, that's what most of the RV and box truck upfitters install on Ford and Chevy cab-chassis.
Ryder Fleet Products is one of the less expensive sources for replacements, but not repair parts. Theirs will likely be black and not have all the features usually put on the RV mirrors, so not an exact replacement.
Here is the tricky part. The mirror mounting changed 2003 E-series model year. So if your 2003 motorhome is on a 2003 chassis, you can use the 2003-2016 mirror. If on a 2002 chassis, you need the 1992-2002 mirror.
Glad you made it! There are a few threads here about those Velvac mirrors. I felt badly that our entry level 2003 RV (on 200TWO chassis, thanks for that tip, Tom!) did not have those mirrors. We have the box truck/rental truck tripod mounts. They aren't power adjust, they aren't heated, but I've added lights and LARGE wide angle supplemental mirrors to them. We have a really great field of view and they don't break. I think the problem is, Velvac uses pot metal for the pivot tube that lets the mirror fold. They press down on a spring and detent washer (that provides the stops when extended) then crimp the pot metal over that washer. The pot metal gets tired over time with use, folding, vibration... Then it loses its tightness on the washer and wobbles or won't stay extended. Then also, it may come totally un-crimped and the mirror arm drops. I've thought up a fix but haven't had a mirror to try it on: Find a threaded tube (thinking of a pipe nipple or the threaded tubing that's used in light fixtures) and epoxy it into the original pivot tube. Or drill the tube out some to get the new piece to fit, but epoxy it to where enough thread sticks past the detent washer that you can use a nut to simulate the crimp. By that I mean both hold the mirror together again AND compress that spring so you have detent. Being tubular, the repair part lets you run the adusting/heating/lighting wires. Either saw the tube off for an OEM look, or leave it extended to ease future repairs. If there's no wiring, could use threaded rod instead of pipe or tubing. As I said, never tried it. Just a picture in my mind.
Thanks j-d. That sounds like a reasonable repair. I haven't had a chance to investigate. I've got a few weeks to repair or replace the mirror. Now that I'm home I have access to more than duct tape and bungee cord. I'll let you know how it works out.