Shameless plug, but Dave @ DPD makes really good antennas. Prices are very reasonable for the quality you get and they will last years.
Specs Gain: 7 dBi SWR: 1.5:1 or Less on Center Pattern: Omni-directional Wavelength: Multiple 1/2 Tuned: 851-869 MHz Band: 800 MHz Safety Connector: N Female Cable: RG8X Cable Length: 24 Inches Height: 57" Width: 1 1/4" Weight: 2 lb Wind Area: 0.50 Sq Feet Features Ready Made...
dpdproductions.com
If you want a broad coverage antenna (but less gain than the DPD) then I'd suggest the Diamond D130J discone:
Diamond D130J Diamond D-130NJ Discone Antenna
Just be sure to use quality coax cable (LMR400 would be ideal) to get maximum performance.