Passenger side convex tow mirror source

I gotta do something about the passenger side visibility on my old dually. Originally it had the stock small towing mirrors which were worthless. I upgraded to a cheap set of the big rectangular tow mirrors, but they're flat mirrors and visibility is still limited.

I've tried the convex stick-ons, and they just make it worse. Yes they widen the field of view but the image is too small to make anything out. I need the whole mirror to be convex like a normal vehicle.

In looking for a convex mirror I am having a hard time finding definitive information. Does anyone have a link to a passenger mirror that is FOR SURE a convex mirror?