Since you are trying to save money, you do not need a pH controller: just a regulator, needle valve, bubble counter, and reactor. Nowadays, most regulators come with the needle valve and bubble counter. This is where you do the happy dance. Barring private offers, there are several current commercial offers: JBJ Regulator
- fixed pressure and is attractive www.aquabotanic.com
-- free ground shipping for APC members www.ebay.com Milwaukee Regulator
- adjustable pressure and is less attractive http://aquariumplant.com/cgi-bin/cart/pr007.html
-- it has the lowest price right now...until supply last... www.glass-gardens.com
-- 5% discount for APC members and is currently offering free ground shipping for www.plantedtank.net
members External CO2 Reactor
, if you have a canister filter
Do-It-Yourself -- not difficult and costs about $15
Have-Someone-Else-Do-It-For-You -- www.glass-gardens.com
-- if you buy everything from here then speak to the webmaster and s/he may be able to provide you with a deal.
There probably are others but I am not familiar with them.
Now is PERFECT time to go pressurized with all these offers flying around. If money is an issue, then carpool for a week to save gas money and direct the funds here.