I thought I'd provide a bit of history on the Inder trailer as I know it....
Inder is an Indian company that built the trailer in the Punjab region. They were large LML dealers, which is the company in India that makes the Stella. They were available in the U.S. for Royal Enfield motorcycles but people have connected them to other powered two wheelers (PTW). I have no idea how many were imported into the US but it wasn't many. I don't know when they were first manufactured. As far as I have been able to understand, Inder stopped making the trailer in 2008 (I've forgotten where I read that years ago). Mine is a 2003 according to the tag on the bottom of the trailer. It weighs about 50 lbs empty.
The Inder was inspired by the PAV 40 and 41 trailers, built for Jawa and other motorcycles in Czechoslovakia, starting in the 1950s. The PAV trailers are no longer made either.
I bought the Inder from a guy who was an MV member but he moved to Brazil and hasn't been heard from since. Before he left, he was the sales guy and at one time the service manager for San Jose (California) Vespa/BMW/Zero Motorcycles. Prior to that he worked for Piaggio or Vespa and was, I think, the rep for the western (US) states. He had a garage full of Vintage Vespa and other scooters.
He told me he was visiting a Vespa dealer in Oregon and they had this one on a shelf. He said they gave it to him. I asked him about registering it with the DMV and he never did.
I called the California DMV about registering it. I told the woman I spoke with that it was about the size of a small shopping cart. She came back after 15 minutes on hold and said I didn't need to register it. So I didn't. I did move my Vespa license plate to the Inder to avoid suspicions. But no LEO ever gave it a second look AFAIK other than curious about it's uniqueness.
I've never seen another Inder scooter int the flesh. Over the years, a few people have posted their Vespa with an Inder and I've found a few pics on the Internet with them but they are rare indeed. Capt. Gary has had his for a number years and he was quite helpful to me in understanding what I was getting into when I bought it.
There's a few other companies that make one-wheel trailers. But none of them have the vintage look of the Inder or PAV trailer. They all lean with the bike and have a hitch that like u-joint like hinge so the trailer moves both up and down relative to the bike and pivot side-to-side for turning.
Here's a bunch of pics of both PAV and Inder trailers.
Enjoy! Miguel