I played through the entire game and was unable to find them, I checked after every mission I did. The only thing I can assume is that it may require the Hanar Diplomat mission, as that is the only one I didn't do (not my choice.. the bug happened to me). Where are them?
I'd also like to add that I thought it made sense that this mission needed to be completed because I have read that the guide says you buy them at the hanar store.
Best Answer
You can buy the Hahne-Kedar arms in the Kanala Exports store. From here:
And from the ME wikia:
I'm only seeing one other claim about this: