Reddit mentions of Chantelle Rive Gauche T-Shirt Bra, 34A, Cappuccino

I have the same problem, and wear the same size (when I can find it). I don't need a bra that feels like a tank for my average-to-small bust! My favorite light bras are Natori Feathers Plunge, though the closest it gets is 30D. The cups run a little small, too, though I don't mind it too much. The lace tunning part of the way up the straps may also give you some issues with a camisole. A lot of Natori's bras seem to run toward the light, thin, stretchy side, so you may have luck with any number of their bras. I think the smallest they go is a 30 band.

The Chantelle Rive Gauche t-shirt bra also has nice fairly thin straps, and the split strap design is pretty and would blend in with camisole straps, I think. Again, I think this only goes down to a 30 band, but it's one of my favorite bras. I have this one in a 30DD/E and it fits well, so I guess it runs one cup size small. My underbust measurement is snug:28 and btt:25.5, so if you're around there or bigger these bras should work alright for you too.