If you go to the [Thirteen] main store, you'll find a lovely poster advertising "Custom Top Matches by Thirra Huntress". Ms. Huntress offers her services creating textures that will let you wear a top of your choice with eCorp prim breasts. The notecard that the poster will offer you if you click on it gives details; some tops are more difficult to match than others.
It's good to see more people offering this service. Thank you, Thirra!