yeah, the 2800 crystal deal sounds like your best bet.
Otherwise, if you're needing the Stun Cuffs but having everything else for the equipment, stun cuffs are constantly cycling through various stores and are also available to farm from normal nodes in LS/DS and Fleet battles. Putting off all other farming, you can get:
240 LS/DS energy/day normal
45 x 3 = 135 energy/day bonus = 375 LS/DS energy, or 37 attempts at a stun cuff node.
3 x 50 crystal refresh = 360 energy = 36 more attempts.
Fleet energy gives you 240 normal + 45 bonus = 28 more attempts
3 x 50 crystal refresh = 360 energy = 36 more attempts.
In 24 hours, you should be able to get about 135 attempts. This should get you a low of 20 and a high of 45 stun cuffs.
Together with other sources of stun cuffs, even though it's random, you might be able to get 50+ total or you might get stuck around 25-30 with bad luck.
But you have 34 hours left for Malak, which means you can get in an extra 3 refreshes of each kind of energy. Drop Rates were lowered in Fleet when they doubled the energy recovery rate, but that's still an extra 10 stun cuffs easy.
Now you're at 35-40 stun cuffs gained in your worst case scenario. All this for 600 crystals (which is much less than 700 crystals per 25 in the store), and you get your first 25 for only daily energy + 300 crystals.
So assuming you only need stun cuffs, one day of solid farming + 300 crystals should get you at least halfway, with a possible 700 crystals to buy 25 more stun cuffs from shipments if you needed a full 50 salvage and got bad luck.
That's 1000 crystals total, which represents a huge savings over the 2800 crystal option.
Again, you might need Mk4 Holo salvage too, in which case maybe just spend the 2800 crystals (and spend cash to get the crystals, if you need to), but if not, I think you can do this pretty handily. Most players at this level have 1000 crystals laying around all the time. (I almost never dip below 5k, and I spend them rather than hoard them). So I hope something like this strategy will work for you.