I think you may not have hit the filter correctly. :) (Go to Apparel-->Tops-->Bras. then go to the size filter and click "See More Sizes") There are 4 bras in 38B on the site:
http://www.teamestrogen.com/product/...00002~38B.html For best support in a racer-back, I'd recommend the Moving Comfort Juno over the Saucony Motion Sensor.
As for B/C, yes, there are some options here. I find Cs a skosh too large in some styles (I can hardly believe I'm writing that...:D ), so here's some B/C options that I've found to work well.....
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Hope this helps!
Susan