Handguns are really difficult to come by as of 02/2013.
Even for armed professionals(sworn LE, corrections, private security or protection specialists, etc) the prices & selection(available choices) may be difficult to deal with.
From what you posted so far, I would highly suggest a simple, robust well engineered DA only(hammer fired/no hammer spur) pistol in 9mm or 9x19mm, .40S&W or the more powerful .357sig caliber.
The .357sig would be my 1st pick because it's well engineered & feeds(cycles) well with most ammunition brands. It's not as popular as the .40S&W for sidearms but it's used by many major federal/state/local LE agencies; Texas DPS, US Secret Service, FAMs(air marshals), NM State Police, VA State Police.
For firearm brands or models, I'd check the HK P2000 LEM, the SIG P229R DAK, the PX4 C format(.40 or 9x19mm), the S&W SD9 or SD40(a striker system but full DA only), the new Walther PPX in 9x19mm.
I'd get the new sidearm fit with 3 dot night sights(for low light events) & a 1913 or rail for white lights/laser aimers. New green laser systems are out there. They are not cheap but worth the use under some applications. See Lasermax & Crimsontrace;
www.crimsontrace.com . Some forum members may suggest a Glock or XDm which are top choices but I'd go with a SIG, Beretta, HK, or S&W first. Know too that you could buy a compact sidearm than get a sub-compact model to use for off duty/2nd gun use. The firearms could share duty magazines too. Like a P2000 & a compact P2000sk. Or a SIG Sauer P229R DAK & a new P224 DAK in .357sig, .40 or 9x19mm.
Keep your new firearms clean & check them often. Use a top CLP(clean lube protect) like LPX, Gunzilla or Weaponshield;
www.brownells.com www.gunzilla.us .
For duty ammunition see; Ranger T/T Series Speer Gold Dot or the new Critical Duty line(9mm 135gr +P, .40 175gr).
Stay safe out there!
CF