Jessica Biel & Justin Timberlake Shop for Jewelry in N.Y.C.

Jessica Biel and Justin Timberlake

PA/Landov

Before their glam night out at the Met Gala, Justin Timberlake and Jessica Biel scoped out some accessories.

Stopping by jeweler Eli Halili in New York City's SoHo area, the couple "spent over a half hour" in the store, an onlooker tells PEOPLE, adding that they worked with the jeweler and picked out ancient rings, precious stone necklaces and even tried on wedding bands.

"They definitely seemed fond of each other," says the source. "They were extremely personable, comfortable and relaxed. They weren't holding hands or anything, but they just seemed comfortable with each other."

The engaged couple left the shop with a 24K gold ring and two necklaces, totaling almost $7,000.