Wal*Mart has a selection.. Just out of coursity (The cat survived) I checked the page.
They have some that have a 300 Pound capacity, are not very expensive and look like the one my Wife had. IT WILL fit through the door of my RV, though I carried it on a modified cargo tray (The tray is not wide enough) when she was alive and we had no car.. Once we got a car she died, I disposed of it.
THe larger ones I do not know since I've never checked.
And some of the "Three Wheel" jobs are even smaller.
Some of them "Break down" Meaning you can take them apart in to smaller sub-assemblies with a simple latch or 3 and put 'em back together again.
Lots of options.