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.

Brassiere with a Low-Cut Back Beige tulle bra with low back

Bras For Different Types Of Dresses - Low Cut, Bodycon

Our Sew In Cups are firm enough to give support and shape and the edges are soft enough to easily sew through. SIZES : A, B, C, D (SEE SIZE CHART TO

SEW-IN CUPS

List of bra designs - Wikipedia

Backless Bra. Halter Open Back Bralette. Bra for Backless Dress

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

Open Back & Backless Wedding Dress Styles of 2024 + FAQs

Tips For What To Wear Under Your Wedding Dress

What to Wear Under Your Wedding Dress - The New York Times

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