Fellow shallow breasted person here.

In addition to Natori Feathers, I like the plunges from Chantelle/Passionata.

https://www.amazon.com/Passionata-Chantelle-brand-Brooklyn-T-Shirt/dp/B01C2CTBPI

I personally haven't gotten around to trying the one linked above, but I remember it working out for several shallow folks about 2-3 years ago (my info is a bit dated, my apologies)

There's also Natori Flora- which I like way better than the Feathers, the cups are a touch shallower.

Give these a try, if you need something even more shallow, you might have to go the Pepper route, which I don't love recommending because their sizes are forked. They are the shallowest bra I have tried on, but I had to buy/exchange a bunch of times before I got my size right. I do think their product is good, they just need to rethink their marketing and sizing.

GL with your bra search! <3 Feel welcome to reach out directly if you need more suggestions. Chances are, if it's a shallow bra, I've tried it on at some point lol