Rose and I got our hitches from
HitchDoc and are very happy with them. Mine is chrome and meant to fit a Valk Standard or Tourer. You might need to get the Goldwing hitch for an I/S, not sure. At any rate, we've been extremely happy with those hitches. They installed pretty easy, although Rose claims that wiggling the bags back into place on my bike was a challenge. I'm not sure that's the fault of the trailer hardware, though.
We bought our trailer from
MotorcycleTrailer.com and are likewise happy with it. We bought their SUPER-basic, build-your-own trailer base. It consists of a metal frame (which I like a helluva lot better than comparable models sold at National Tool, Home Depot, etc. because it uses rectangular steel instead of u-channels) with wheels/tires and lights and wires. We provided our own plywood base and bolted a big plastic dog carrier to the top of it, and we take our dogs with us on trips. They have several versions of these do-it-yourselfers with varying cost and features, along with plenty of finished trailers and some used ones, I think. They were pleasant and honorable people with whom to do business.
I found that we needed an adapter to make the trailer lights work "properly" because of how the Valk (and Rose's Yamaha) are wired in the brakes/blinkers department. It was
this thing which we put inline between the bike and the 4-way flat connector so that blinkers and brakes worked as expected. My memory is hazy now, but I think that without the adapter, both blinkers on the trailer flash at the same time, regardless of which way you've thrown your turn signal.
Anyway, YMMV, but that's what I've found and enjoyed. And recently, someone posted the following summary of lots of different trailers, which might help your shopping process:
http://www.bidouilles-on-my-wing.fr/gb_remorques.html