Depending on the options on your TB you might be able to mount it in different places, for example the overhead console if you don't have a sunroof or homelink/voice recorder. Under the dash (ie. by your left knee)
Here's a pic I found
You should go to
Trailvoy.com - The Chevy Trailblazer and GMC Envoy Enthusiast Site, there's a lot of people there who have radio equipment mounted. And here's the topic where I got the picture
Hello Moto - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum
Edit: I forgot to add, I did not drill any holes for my installs, if you're willing to drill holes, it'll be easier to mount on the console (the curvature of it makes it a PITA to use double sided tape, so there's only a few spots where you can do it).
I'm actually looking to get an extra console from a junkyard and use that one to mount the equipment. I'll probably get more soon anyways.