For towing our 30' travel trailer, I bought some cheap clip-on mirrors from Amazon at about $13 each.
K Source Clip-on
CIPA makes similar ones:
CIPA Clip-on
They served their purpose well. I am able to put them on and take them off very easy and at no time during the entire summer of towing did they even remotely seem like they were going to fall off. The downside to them? Well, they look exactly like what they are: cheap, clip-on mirrors. That doesn't bother me, though, and I'm not worried if anything happens to them. Plus, removing them as soon as I unhook the trailer is really easy to do.
I've seen the custom towing mirrors on another Yukon and they do look nice, but I have aftermarket chrome covers on my side mirrors so I don't think they'd fit on my vehicle very well. Also, the mirror itself doesn't look that much bigger so I don't think I'd get any better performance with them over the clip-ons.