In the past, on a smaller discovery board, I used "Aries Electronics" 04-003-173 which can be obtained from Mouser. It was a nice little cable that allowed programming and ICE features of the SWD interface.
http://www.mouser.com/ProductDetail/Aries/04-003-173/?qs=kYCaYsuokbDi56RYUcOd53WdGkJVC2XrWHBfbDlnssI%3d
STM flat programming cable
STM flat programming cable
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