Thanks for the info Spawnflagger, I wasn't aware of this when I wrote those links. Actually none of the cards I linked to have been tested on Jetson TK1, I only know that at NVIDIA they tested a few mini-PCIe cards and those did work but I don't know what cards they actually tested. So I just did a search of various mini-PCIe cards and posted links to them.
I'll move the links to a separate page "http://elinux.org/Jetson/mini-PCIe" with the info you posted here, and keep full-height and half-height mini-PCIe cards in separate sections. If you end up finding other useful half-height mini-PCIe cards, feel free to add it to that page, mentioning "(untested)" or "(tested)" if you do actually test one. (Note that some devices will need kernel or firmware driver support before it works).
Thanks Shervin. I will be getting a Jetson TK1 soon, and have also ordered a Syba half-mini PCIe Gigabit NIC (Realtek based). I'll report back to confirm/deny that it works. The full-card to half-slot adapter/riser I mentioned is this MM3U+DB3U (untested).