You could make your own "plug" per say but I don't have time to explain it all with pics as I'm out the door right now. If you can't find anything else i'll help you make something work.
So they only sell it as a large wiring harness I take it? If you call around, a junkyard somewhere will have a 9th gen. Surely you could go clip that plug off a car. Another option is contacting someone on eBay. There are quite a few people who sell off salvaged cars piece by piece on eBay. You'll figure it out when you see a billion different parts of a 9th gen in their eBay store. Shoot some of them a message with what you need.
Can I order from them?Almost everything out there is a replica. Kingmotorsports is the only authorized Mugen distributor for the US.
http://9thcivic.com/forum/threads/announcement-of-new-mugen-parts-for-9th-gen-civic.8183/
The replicas have all had bad reviews over the middle top portion flexing and shaking while you drive. A handful of people bought them and removed them due to quality issues.
They don't have it listed on their site to buy, but you could contact them. Part of the problem is that the car design is based off the Asian market civic. They don't have the si, and there are body style differences. They may still be able to sell it, but be prepared to pay a heft sum for it. Mugen parts are not cheap.
What happens to it?
Trade it for an ap1 s2k with 30k original miles, someone crashed my s2k got it fixed but didn't feel the same ended up selling the s2k now I'm back in a 15 Si but it's a modern steel metalic color.