Can't really recommend any particular make and model -- just search for Probe Thermometer in Amazon. You don't need anything fancy. A simple stick thermometer will do for spot readings. This one is popular with HVAC techs:
http://www.amazon.com/RT600C-Super-f...dp/B002GE2XF8/. One with a flexible probe is useful for measuring temps inside racks or equipment. This one has min/max recording capability:
http://www.amazon.com/General-Digita...dp/B001TOJGBK/. For data logging, I like the HOBO series from Onset:
http://www.onsetcomp.com/products/da...rs/temperature.
Hope that helps.
Ken