CB help

[working Hummer]

I'm going on a Hummer Trek and need to install a CB quick. I'm just buying a $49.00 cb from Radio Shack but here's my question, my installer said he should mount the antenna on the back roof away from the other antennas but he didn't know if they make a window ones like a cell phone antenna that would look nicer also if they make a short rubber one for the roof. I dont want a magnetic one because I heard they suck, also I don't want a 5' long metal one there either so does anyone know if they make a good short rubber one or am I obligated to a long metal one. Any help or opinions would be appreciated. thanks