So after calling numerous stores I have found out that practically the only place to get Turtle Beach's "Talkback Cable" is on the Turtle Beach website. Figuring out that it was simply a 2.5mm Male to 2.5mm Male audio cable, I figured if I called around about that I would surely find what I'm looking for. That was a no-go.
I'm actually quite surprised. Here I thought there was a cable for everything! But apparently you need an adapter, which brings the price above what I'd have to pay if I just bought it from Turtle Beach.
TLDR: If anyone knows of a place to buy a 2.5mm Male to 2.5mm Male audio cable for less than $15 shipped, do let me know!