Last August, someone else was asking where to get replacement SATA cables for the same model that you have. The advice from an Intel support staffer was to contact Intel customer support directly to request a new daughterboard, making sure you tell them that you need the SATA cables as well.
Here's the original discussion thread.
I did some extensive research on your problem. I wasn't able to turn up any potential sources for the cable, other than cheap NUC units on sale on eBay.
Somebody else had a problem with your model - they found that the SATA cable was non-standard pins and ordinary SATA PC cables wouldn't work with it. so they came up with an interesting workaround where they removed the NUC's HDD caddy and replaced it "with normal SATA data cable and an external SATA power cable to power the the SSDs."
In the same article, a commenter said they had found an alternative cable at MicroSataCables' eBay store that was a perfect fit. the item they linked to is no longer on eBay, but the description was: SATA 22 Pin Female to 7 Pin and 15 Pin SATA Power Female - 12"
I looked on MicroSataCablesUSA's full web store, and the matching item seemed to be this one. Does it look familiar?