I too made the purchase of the Triumph aux adapter, only to read thru many threads (before my item arrived) that it is only compatible with Triumph accessories. I went to the local auto store (Oreilly's) and purchased a weatherproof outlet that would accommodate most other practical items out there in the world: cell phone charger, power adapter for music items, 12 volt air pump, cigarette lighter, etc. It was 1/3 the price. I'll never be able to return the adapter (at least I don't think) but maybe I could get some of my $$$ back by selling it.
Haven't installed the adapter so I'm not certain if there is a plug-in specific to the Triumph adapter. I was thinking of installing both but I can't foresee myself ever purchasing an accessory that would use the Triumph plug.
Live & learn.