If you can stretch i little more on the budget then Hanna make some very good meters, very reliable and excellent quality
HI-98100 Checker Plus pH Tester
The easy to use Checker plus is a real favourite with students and researchers due to its clear LCD display and long thin pH electrode. The checker offers automatic calibration and buffer recognition, calibrated buffer tags, and a stability indicator.www.hannainstruments.co.uk
How long do these PH meters last for?