I recently got the Burley alternative QR hitch for our trailer...had to wait a few weeks until it came into the country - importer is getting all the spares just not the actual trailers. I spoke to my LBS and they put it on order and it arrived at the shop, the day before it was actually due in the country with the supplier! I was chuffed but it wasn't cheap.
I'd offer you our standard hitch but it fits the other bike so it is currently sitting on that waiting to be used.
Ebay might be an option? I've now forgotten the importers (I'm wanting to say Fisher but I don't think it is), but give them a shout and they can tell you if the parts are available and then you just contact a shop that deals with the supplier, they put the order in and you get the bits.