I frequently carry my Colt Defender, the same size as a Kimber Ultra, in a "Compact Under Cover" holster from Kirkpatrick in Texas. This is an OWB belt scabbard holster that was designed for short barrel 1911s. It holds the gun high on the belt at a good cant angle for concealment. Here is a photo of the gun in the holster:
Kramer also makes a nice belt scabbard holster in horsehide that is very stiff for easy reholstering. I use one of these for a Kimber Pro CDP, a slightly longer gun than the Ultra:
