What type of professional can I see to get advice about retirement accounts as a US citizen residing in Japan?

I'm a US citizen living in Japan with a Table 2 SOR for over 5 years and working at a Japanese company as 正社員.

Currently the only retirement saving I'm doing is investing a portion of my post-tax income into index funds on a US brokerage account, which seems inefficient.

I would like to make sure I'm taking proper advantage of the retirement planning options available to me. I've done my background research online about the different vehicles available in both Japan and the US (iDeCo, NISA, 401k, IRA, etc) as well as domestic and international tax complications including PFIC issues.

Although there is a great amount of information available on the internet and on this sub, ultimately I would like to pay an expert that deals with Japan/US tax planning all day to to assess my situation and advise me on setting up the best plan for me.

However, I'm stumped on who might be qualified to advise me without breaking the bank. I assume that the big 4 could probably do this for me, but my understanding is that they would charge me thousands of dollars just to have the discussion, so I'd prefer to go with someone independent.

So, how can I find a professional that is qualified to advise me? What sort of licensure or background should I look for?