Just curious, why do you care about SG faction; I thought everyone was KOS?
But to answer your question, as
the wiki helpfully shows, Siren's Hair also drops off of the sirens in Cobalt Scar, who don't (at least according to the wiki) hurt SG faction. Watch out for their charm though
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You will inevitably have to go into SG for Shawl 7, at least for the Swordfish Tooth, and possibly also for the Molkor Hide and Runed Sea Shell ... but the Swordfish Tooth comes from fish who shouldn't (again, according to the wiki, which could be wrong) hurt your SG faction, and the other two are droppable so you can buy them off of other players.