Can you recommend one for about $200 Plus calibration which I view as essential.
Sorry for the delayed reply. I hope you see this, emergingsoul.
I currently use a TSI/Quest Sound Examiner SE-402IS. I have a Quest QC-10 calibrator for it. My best suggestion is to get a sound meter/calibrator from the same manufacturer. That way, you're ensured to get a calibrator specifically tailored to the configuration of your meter. If you decide to go with a stand-alone calibrator, I'd stick with one manufactured by companies that specialize in analytical instrumentation. If you don't need that level of accuracy, then any sound meter in the $100-$150 range should suit you. You'll likely want one that fits both the 1/2" and 1" microphones most good sound meters have (one or the other). Just make sure you know what size microphone your meter has.
If you're talking about phone calibration, as far as I know, the only way to do it is to compare it's reading with a true, calibrated sound meter. Remember, phone apps are nothing more than rudimentary screening apps. That said, 20-30 dB difference between apps seems like an awful big spread. I'd be inclined to think that the NIOSH app has a better algorithm. Here's a study on phone app accuracy, albeit a bit dated: https://blogs.cdc.gov/niosh-science-blog/2014/04/09/sound-apps/
Luck.