We picked up a couple that expand from an online site called Downtown Pet Supply for only $20. They are pretty lightweight, but I noticed that the Good2Go ones at Petco appear to be even lighter weight. The Sherpa ones felt heavier to us when we were looking at them. We opted for the medium sized one from that site which unfortunately is also a bit over what the airline lists for dimensions, but we're hoping that they'll treat it as they do duffel bags that can compress in some areas. We're flying out in a few hours so I'd be happy to post an update about how it all works out. We found that the collapsible bowls from Amazon (2 for $3) are pretty decent and come with a caribiner clip. In the past, we've also had good success with buying a couple of puppy pads for the inside, just in case. We called the airlines and were also told that we can take one of those throw away litter boxes that come with litter and some dry cat food in a ziplock bag.

I wish I could make a better suggestion about the carriers specifically for Delta, but I think so much depends on how crowded they are that day and who happens to be handling the gate. We've noticed that on 1/2 empty flights they often don't even glance at your baggage, so I assume that it's a similar situation when traveling with pets.