Another camper noob question - window to truck?

We have a slider on our truck and a removable window on the TC. We made our own "boot" to go between the truck and TC. It's a fairly small opening, but it works well for our pets and they use it quite a bit while we're driving.

I have no idea what a replacement window would cost for your truck. It might be something you could find in a junk yard if not aftermarket.