One of my favorite pieces of brewing equipment and a trustworthy, well-built one is a TM500 Palmer-Wahl instant read thermocouple meter. I've used mine for six years now with complete accuracy, and it is so easy to use, to accurately and very quickly measure temps for everything from hot liquor, sparge water, mash, sparge, hydrometer flask, chilling wort, wort at pitching, etc.
http://www.palmerwahl.com/product_home.php?cat=3&catl=43&line=12&itm=604 Along with it, from McMaster Carr I got an 18" flat pin stainless steel immersible probe. Looking at the website the part appears to be: 316SS Air/Immersion Thermocouple Probe Mini Conn, w/o Cable, Type J, 32-1400 F, 18" L Probe, part # 39095K62 that is around $20. If you get the 18" or longer probe it will sit in a bucket of sanitizer with the plug-in end still above the solution, for easy reinsertion into the meter when you're working on the cold side.
http://www.mcmaster.com/#flat-pin-thermocouple-probes/=i073vp