Indian Space Research Organization - Extent of spectral spread 1/3rd Octave Analysis
That's not really a signal processing  question, but here are are some pointers.
3rd octave filters are well defined in ANSI S1.11-2004 and any decent commercial implementation should be fully compliant to the standard. The implementation is rather simple, so compliance isn't much of a problem. It's easy enough to do it yourself and their are ready-made packages in analysis products like Matlab https://www.mathworks.com/help/audio/ug/octave-band-and-fractional-octave-band-filters.html or measurement products like B&amp;K https://www.bksv.com/en/instruments/handheld/sound-level-meter-apps/bz-7132-and-7131-frequency-analysis (no product endorsement intended, but these are reputable names).
One thing to keep in mind: In most real world acoustic problems, the difficult part is NOT the analysis but actually making the measurement and/or data capture. Where and how to place what type of microphones, when and how to capture with what signal, making sure that the signals are neither overdriven nor overly noisy, good signal to noise ratio at all frequencies of interest, good reproducibility, etc.. This requires fare more experience and expertise than the data analysis, so if you want to spend extra money, I recommend you spend it there.
Sound fields are very complicated 3-dimensional phenomena and a microphone only samples a single point in space. Moving a microphone by a few centimeters often makes much more of a difference than any analysis parameter.