Volkswagen stopped producing the Thing in 1980, and shortly after, they stopped making new VW Thing parts and accessories. If you are restoring one of these unique cars, you can still find the parts you need if you do some research. The last of the production run is over forty years old, so it will take some persistence to find what you need, but here are some places to start.
Shopping For Parts
Anytime you are dealing with rare parts for a car that is out of production, you will need to search to find the right ones. The manufacturer only imported the VW Thing to the US for two years, and because of that, most of the parts stayed in Europe with the cars making them hard to find.
While there are still companies making reproduction parts for these cars, the first place you may want to look is online. A quick search with an internet browser will turn up some online businesses that still have VW Thing accessories, and many of these companies are reproducing parts for these cars because they could not find them.
Because many of the parts available are not from the factory, it is crucial to check reviews and information for the parts so you are sure you are getting the right parts for your model year and that the parts are of good quality. A part that does not fit or function properly is not worth buying, so spend some time researching the company and the parts they offer before you purchase parts from them.
Swap Meets and Flea Markets
Sometimes a car club will hold an event that has a flea market or swap meet. A VW club event, especially one with many members with older cars, could be a great place to find some VW Thing parts or accessories that someone has been holding onto for a while.
Take any parts that you are not going to use with you to offer them for sale or as trading stock for parts you need at the event. Often someone with a rare part that you need will be willing to negotiate, and if you have something they need, it could be more valuable to them than cash.
Make sure you check with the event organizer if you are planning on selling any old parts at the flea market, as sometimes they will require you to rent a booth or spot to offer your parts, but just attending the event allows you to buy and even trade parts at most shows.