I traveled w/ my fuzzies this past month..I bought a cockatiel ranch style bird cage, at Petco 20" X 16" X 29" tall..It fit nicely in our motorhome..and the tray slid out, on the bottom, to make cleaning easy...I put the Wodent wheel on the bottom of the cage, then attached the top..worked great.
They had enough room to romp, and lots of exposed wire top, for tummy tickles..They even seemed to enjoy the perches that came w/ it.