You would need a
CO2 Regulator and a
PH Controller.
I for got I have a PH Controller / Monitor, You would just have to get a new probe for it.
Link to Probe
I'll add the controller to make it $200 even, then all you need is the
Regulator and
Probe, if you want.
I'm leaving town on Thursday till the 16th, If you really wanted it we could figure something out otherwise after the 16th.
Cheers