We use Performance Review Institute (PRI) and have been happy with them. They are reputable and rigorous and over the many years that we've used them I think we have only had one auditor that we felt did not do a good job. https://p-r-i.org/
I printed out IAQG OASIS list of accredited registrars but can't attach it - connect with me on LinkedIn if you cant access it from Duke Okes link.
With members and customers in over 130 countries, ASQ brings together the people, ideas and tools that make our world work better.
ASQ celebrates the unique perspectives of our community of members, staff and those served by our society. Collectively, we are the voice of quality, and we increase the use and impact of quality in response to the diverse needs in the world.