I believe SDKs are approved for wear, but the NEX is still getting spun up to supply them and they won't be available until at least next year.
Depends on which NEX, the Navy Annex one in Arlington doesn't seem to have a problem getting them for some reason.........last time I was there the lady helping me had to cut it short because she had to get ready for the first of two Admirals getting fitted for one that day.