Talked with my local Subaru place, they couldn't find a replacement harness for the sub.
So I called Kicker and they do have the harness along with all the replacement parts, but Subaru will not let them sell individual parts from the kit. But Kicker did have the part number that Subaru uses. Called five Subaru dealerships in upstate NY and the cheapest I've found it for was $129.00.
'08-'11 Sedan w/o NAV
I got the sub for next to nothing, so I figure $129.00 is a great deal a genuine Subaru accessory that retails for a MSRP of $499.99. Would have liked to make my own harness, but the factory harness has the correct high pass filter in-line, is plug and play, and up to Subaru's quality standards (most likely better than I would have made).
I wasn't ever planning on getting subs for the car, but when a good deal on a factory upgrade part comes along it's hard to say no. Especially since I just installed Subaru's media hub and new poke 6 1/2" component front door speakers and poke 6 1/2" rear door speakers.