There is a possibility that acidifiers cause or assist in causing feline idiopathic hypercalcemia, so I would only use as a last resort.
Meat produces an acid environment, the one natural to a cat. Any wet high protein, low carb diet would help. Naturally, a raw diet (w/o vegetables and fruits)...
Unfortunately, canned food can be very expensive.
I suggest you start off with the canned food you can afford. Then calculate how much it costs to feed your cat(s) per day. Then buy a few higher quality, more expensive cans and feed those and calculate how much it costs you to feed them as...