anyone made window bars for rear window

[blazer2007]

Iwas looking for some ideas for bars on the back tailgate window when the window is rolled down.I know you can buy somthing at the pet store but I was thinking of something on a hinge maybe.I have 2 big parrots and a big dog that like to go car ride and is too hot here in the summer ,no air.I,ve seen them in older movies on Mex border patrol blazers but can,t find any pics. thanks