Thanks for all the great suggestions--I've tried to check out all the sites suggested.
Here's the main issue: I don't want something as large as a 20-22" carry-on. If I'm gonna spend some bucks, I don't want to deal with what are sure to be even more restrictions in overhead space down the road. So I want something that will fit under the seat if I have to do that. A second issue is I really want a 4-wheeler 'spinner' for easier movement without having to drag something behind due to some recent low back issues. (And I understand the spinners allow much easier movement in the aisles on a plane.)
Unfortunately, I don't believe the luggage manufacturers have caught up with the new sizing guidelines (and per the WSJ article), because I don't see many wheeled models which will fit under a seat, and so far haven't found any that are 4-wheeled to meet UA's guidelines. Turns out the Magellan model I mentioned in post #7 is actually 3/4" too wide on one side. Just not sure if it's soft enough to 'squeeze' into their size-checkers. Rats.
So it appears I'm asking too much, after many hours searching online. I'll probably have to go with a 2-wheeler, or just deal with a shoulder bag, which I really didn't want to do.
And I agree with oceanvps--it's ridiculous how different airlines have different guidelines. Sheesh.
Edited to add: I really don't want to have to gate-check this carry-on: I'll need to carry essentials such as an iPad, prescriptions, blanket, etc. which I'd need to keep close on flights. Plus want to make sure I can use this on International flights. Again, I'm probably asking too much--the product just doesn't seem to be out there today.