I took a look at the pet carriers on Amazon. Quite a few to choose from. I currently have a really ~cheap~ small cage I use for taking the birds to/from the vet, but that won't be the best for anything really long term.
I have seen people use small pet carriers, and I like the idea of covers. What I found is that it's not easy for my bird to hold onto a perch while in the car, especially if my bird is ill. I had a sick budgie, and she used to have one foot on the perch and one on the bars to steady herself.
So I'll have to think about a soft carrier vs a wire/plastic one. I do wonder about my birds chewing through the mesh or how to keep food and water dishes from spilling.
I see your point about food spoiling if it's left for too long. Maybe have containers set up next to the food that I can fill quickly may be the best option.