Just apply for a travel document using Form I-131, Application for Travel Document.

File Form I-131, Application for Travel Document, to request travel documents, including: Advance parole document for noncitizens in the United States seeking to return after temporary travel abroad (including advance permission to travel for Commonwealth of the Northern Mariana Islands (CNMI) long-term residents

The fastest way is as part of the original marriage green card application package you send to USCIS, by including Form I-131 (“Application for Travel Document”) along with the main forms (I-130 and I-485).