Recommendations on bring-your-own metal folding shopping carts

When we go to the farmers' market, we bring a stroller with a big basket at the bottom for carrying our produce. For better or worse, I have quite possibly raised the world's laziest four-year-old who would love to be wheeled around by a parent volunteer for the rest of her life. Yet, someday, I know I won't be able to push the lazy child up the hill anymore. I have tried to warn her that her kindergarten teacher probably won't be willing to do that either, so she'd better start using those skinny little legs she's got, or else they might wither away. So far, she's not listening.

Our local farmer's market has gone now to its winter schedule (on alternating weeks). Now that our CSA is done, I do my best to get to the market regularly, but often its cold and raining, so enticing the lazy kid to come along in the stroller doesn't always work. I envision one of those metal folding shopping carts in my future.

There's no shortage of options. They seem to come in all colors, shapes, prices and sizes. My dad even mentioned he's looking for one so that he can walk to a nearby grocery store instead of driving (woo hoo, dad!!). Do you use a wheeled metal shopping cart? Do they fold well? Do they wear well? Do they have any especially great features I should be aware of?