Lauren Sanchez is going to have a lot more than '27 Dresses' to choose from ... 'cause it looks like she's finally putting together her custom wedding gown -- going out to Milan to do it!

The former entertainment reporter and her soon-to-be husband Jeff Bezos hit up the iconic Dole & Gabbana store Saturday ... spending a couple hours inside the luxury brand's store.

Check out the pics ... the two were shot leaving the store in sleek attire -- Bezos in the all-black 'fit and Sanchez wearing a gray coat over her black top.

While it's not clear exactly what the pair were doing in D&G, it's likely they were putting some final touches on Sanchez's dress for their upcoming wedding ... which many think will be one of the biggest in history.

Several people appeared to be carrying multiple bags out of the store for them ... though it's unclear if that's a wedding dress and suit under those protective bags or just a fancy cocktail dress and dinner suit for some other major event Sanchezos will attend.

We broke the story ... Lauren and Jeff's wedding guest list is out -- and stars like Eva Longoria, Katy Perry and Orlando Bloom, Oprah Winfrey, Gayle King, Kris Jenner, Kim Kardashian and Jewel are all on it.

We spoke with Lauren's brother, Paul, outside a Home Depot last week ... and, he likened his sis' upcoming nuptials to Princess Diana and King Charles' wedding back in the early 1980s.

Hopefully, she's secured the perfect dress ... 'cause it sounds like this wedding's just months away!