Our team made a trade many years ago (forgot with whom) and the part that we got out of it was a custom carrier. It is a frame of powder coated aluminum, with two hadles. Their latching design allows them to be flipped down, turning the carrier into a table for pit working. The way we test our wheels is by "blocking the robot," which is 4 pieces of wood placed under the robot.
Here's a pic of the carrier, just so you can see what it's like.