Eh just because I've seen a lot of new players asking around all the time, here it is:

Either:
Spam E to try and make a second shop window glitch open on its own (the more lag you have, the better)
Or:
E/Esc/E to open/close/open very fast to try and make a second shop window glitch open that way.

Keep trying until it works, it works for the other flashing-selection unbuyable shops as well (contract vendors, ex inanis vendors etc.). I've reported the keycrate problem to Trion but it's been months so I see no harm in posting the glitch-fix here. You don't get anything else from this method anyway.

From a D2013 freeloader,
pH