The goal is to connect my seat heaters to a switched power source. Sounds easy enough, right?

Here's the challenge: I'm using the heater circuit for..... the heater. I have a radio circuit, but that's 10 Amps. Is that enough? I might have the yellow wire from the Coyote pigtail (C160A), but that's 10A as well.

I could tap into the master cutoff, but I would prefer something switched from the ignition key. I'm looking at the RF schematic as I write this, but I'm not coming up with any creative ideas. That's where you come in. Any recommendations for where I can tap in to for seat heater power?