Shielded thermometers are recomended for safety reasons when measuring temperature in streams. Unshielded thermometers often break or are crushed in transport in the "real world".
Armored Thermometer -5 - +45 Degrees Celcius
Cat#1066 $16.80 + shipping (1995 price)
Lammotte Chemical Products Company
P.O. Box 329
Chestertown, MD 21620
1-800-344-3100