I need help finding thick single layer camisoles (no built in bra).

I need something I can wear under shirts that will help make them a bit more modest for the work place.

I have a bigger chest, so built in bras don't fit- the elastic band either cuts me off in the middle of my boobs, or I have to pull the shirt down low, which defeats the purpose. The single layer ones I have found are very thin, so you can still see my bra through them. I have only ever found one thick camisole I can wear that you can't see through, and the tag is so worn I can't figure out the brand (received as a gift, so don't know where it was purchased).

Help!