I'll recommend a good strapless bra.

https://www.amazon.com/dp/B09VSH1D8S?psc=1&ref=ppx_yo2ov_dt_b_product_details

Cheap? Yes. Amazon? Yes. Does it stay in place and keep things up? Hell yes. If you want to find something more high end for your wedding, that's great... but this'll do you in the meantime. I'm a 40DD and it does wonders.