I calibrate my
PH Meters using pH 7 standard solution. You can find it on Amazon and other places on the net.
For the cheap meters with single point calibration, pH7 is about where it's at. That's the zero point of the sensor, so by adjusting there you adjust the entire offset. You can use a pH4 to check the slope of the sensor but there's nothing you can do about it should it be off. Even with the slope being off, calibrated at 7 it'll still be more precise than phenol red and probably just about as accurate.
I've had a cheap one for a while now (got it free with a TDS meter). The biggest issue I've found with the cheap meters is not having a sealed cap to store the electrode wet. No matter what I put in the cap, it always dried out and that led to difficulty calibrating, drift and unreliable readings. It's a toy, but I keep it around to play with just to see how it performs.
A couple of months ago I took to "storing" it by standing it in a beaker with 30ml of electrode storage solution sitting on the shelf. As it slowly evaporates I top it back up to 30ml with DI water every couple of days when I walk past. Since then the cheap meter has been a lot more usable. Still requires calibration more often compared to the good one, but at least the results are now consistent. If I'm after a quick lo-res check (is it between 7.4 & 7.7) I'll use it in preference to rinsing and storing the better unit.
I periodically buy 500ml bottles of pH 4 & pH 7 calibration solution. Recently I found a hydroponics supplier around the corner and they have similar stuff but at 1/2 the price (with the caveat it doesn't come with a calibration certificate). Shelf life on that is 12 months, then 6 when opened, but in reality as long as it's looked after (don't dip in the bottle, don't pour back in the bottle and keep it inside with the cap on and away from sunlight) it seems to last a lot longer (ie my current stuff reads the same as the stuff I have that is 2 years old).
My good meter has a much narrower probe than the cheapie, so I can calibrate that in a couple of 30ml shot glasses. I use the left from that in a small beaker to calibrate the cheap one.
It's more effort than using phenol red, but then FAS-DPD is more effort than the dpd tablet.