I picked one of these up last week from Amazon.com. I've used the HM TDS meter in the past but this one includes a thermometer. I'm finding it really handy to test water in my tanks. I suggest anyone looking for a TDS meter pick this one up.
http://www.amazon.com/HM-Digital-TDS-4TM-Meter-Thermometer/dp/B001RK38LU/ref=sr_1_11?ie=UTF8&qid=1383635531&sr=8-11&keywords=tds+meter
http://www.amazon.com/HM-Digital-TDS-4TM-Meter-Thermometer/dp/B001RK38LU/ref=sr_1_11?ie=UTF8&qid=1383635531&sr=8-11&keywords=tds+meter