The pair have been engaged for several years but have postponed the wedding several times, most recently due to coronavirus pandemic.
Katy and Orlando have spent the last few weeks in Hawaii with family and friends, and the Firework singer was pictured on Monday with the new accessory.
Orlando's 10-year-old son Flynn, from his former marriage to Miranda Kerr, has also been spotted on the trip.
Fans believe the pair may have married in Hawaii
Pictures published in Page Six show the family and their seven-month-old daughter Daisy, shopping on the island, with Katy rocking a baby pink bandana as a face mask, and a baseball cap that read 'Mama.'
Orlando wore a camo baseball cap, and carried his young daughter on his back, with her face covered with a white blanket.
The Lord of the Rings actor first proposed to Katy on Valentine's Day in 2019.
Orlando proposed in 2019
Katy recently flashed her engagement ring, an eye-catching cluster ring which creates the shape of a flower, on American Idol.
The stunning piece is made up of a ruby and eight clear diamonds as the petals. Katy's ring may have been chosen as a nod to Orlando's surname, and it perfectly fits her adventurous fashion sense.
The couple was due to get married in Japan while Katy was pregnant, but due to the coronavirus pandemic, they were forced to postpone their plans.
They are parents to daughter Daisy
At the time, she told the The Mirror: "You can’t plan anymore in 2020 because those plans are always cancelled. We just want to deliver a healthy child. Everyone has to take life one week at a time right now."
Katy was previously married to comedian Russell Brand.
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