Likely your best avenue is to call H&R Block Executive Tax services.

There might be one in your country.

If not, just pick one from any US City. I'm in Austin, Texas + have been using them for years.

They're way cheaper than a CPA + tend to stay current on new tax code, far better than a CPA, as they run internal, company wide trainings, all year round.

You're smart to deal with this up front.

Avoiding US I.R.S. trouble == a very good idea.