Picked up a used Twister T6 for $400 and replaced the gear box for $100 and now its like new again.
Milwaukee Product Documents
The Milwaukee MI59P is the replacement for Milwaukee PRO Waterproof 3-in-1 Temperature / Conductivity / TDS EC59 and EC60 Testers (sold separately).
The MI59P measures pH and temperature and easily slides into the tester fitting then screws into the meter body for secure installation.