If your duvet does not have that you could sew in ties or purchase THESE Duvet Clips that I use to keep daughters twin duvet inserts in place (see what I use on Twin Beds HERE). (nestingwithgrace.com)
Deluxe Balcony Cabins (Obstructed) are 233 sq. ft. and are a larger version of a balcony cabin, include all regular amenities plus a sofa bed, upgraded bathroom products, bathrobes and a premium duvet insert. (dunhilltraveldeals.com)
ROSECOSE Luxurious Goose Down Comforter Queen Duvet Insert All Seasons Solid White Hypo - allergenic 1200 Thread Count 750 + Fill Power 100 % Cotton Shell Down Proof With Tabs (Queen, White) (amazon.com)