Take a look at the Larsen Tri-band antenna. It's only 16.5 inches tall and covers 150-165, 450-470, and 806-940 mhz. It also uses the popular NMO mount. I bought one from Ham Radio outlet for about $25 (?) and I've been satisfied with it. Not as much gain as some more expensive antennas but it works for me, plus it matches my Larsen 2 meter/440 antenna on my truck.
I've monitored the Augusta/Richmond County, Georgia TRS from a distance of approximately 25 miles. I can also monitor Aiken County, South Carolina 450 mhz comms from a distance of 40 miles.