A-cup surgery options

I have very small breasts and I do a lot of running. My surgeon says she can easily do a silicon implant reconstruction for my unilateral mastectomy, but she didn’t have a sample of an implant that was small enough to match my size in her collection of samples or in recent patient images. I’m concerned that the end result will be annoying when I’m running and whether an aesthetic flat closure would be a simpler option for someone with such small breasts to start with. Can anyone relate and what did you decide?