I bought a pair of "bra buds" from Unclockable that feel nice. (edit: I checked and they're available on Amazon if you don't want to order from Unclockable, however I recommend getting them directly so bezos doesn't get a cut)
I'm a heavier gal so I already had a little extra breast tissue to begin with, but they give me a nice lift with an underwire. They also fill a bralette quite nicely, especially if it has an insert pocket.
I am currently girlmoding (minus makeup, still no clue about that stuff) at the park with some LGBT friends and I took them out because it's a bit toasty and the sweat between the silicone and my skin isn't great. Antiperspirants from now on I guess... Sorry tmi...😳
I also have some foam "push up" bra cups from my spouse's "old bra" collection, I think it was a Victorias secret bra... Anyways I cut the straps off since they're too small for me anyway, and am using the foam cup as an insert. It gives me a 2 cup bump and feels natural, and everyone is assuring me it looks fine.
I also got told I look like a 2004 mom 😂