Do a Google image search for "toddler car seat stroller." There are a few options, including one with fairly large wheels, good for more than just moving a car seat through the airport.
I travel alot with my kids and just check in my car seat as luggage. most airlines do it for free. So the kids sit in it on the way to airport, I check it in and take it of belt again when i arrive. Not a huge hassle, but saves alot of money