I used this company My Tap Score - https://mytapscore.com/collections?utm_source=bing&utm_medium=cpc&utm_campaign=General%20Water%20Testing&utm_term=water%20testing%20labs&utm_content=Lab%20Testing
It is pricey but I felt that it was worth it. My RO water came back clean with no mycobacterium found and they test a slew of mycobacteria. I also drink from a LifeStraw bottle and change the filter regularly.
Good luck!
Carolyn