Cups sewn into dress or plunging back bra?

Does anyone have any experience with cups sewn into their dress or with a plunging-back bra? My dress is too low-cut in the back for a regular strapless bra (see below), Page 2.

The 15 Best Wedding Dress Bras & Where to Buy Them

Adjustable low back bra strap converter hides bra straps

What Kind of Bra Do You Wear to a Bridal Fitting? : Wedding Dresses

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Alterations Help! Can You Get a Bras Sewn Into a Dress?!

Dritz Molded Foam Bra Cups, B/C Cup, 1 Pair, White

Looking for opinions on what bra to wear with my wedding dress

6 Steps to Sew Bathing Suit Bra Cups

How to Sew Bra (Bust) Cups Into Any Blouse Or Dress

Open Back Bra. Wrap Around Backless Halter Bralette – Tatiana's

List of bra designs - Wikipedia