One of my very favorite accessories is a very unique watch/key fob.  It's the only one I have ever seen, and I have a letter from the family I purchased it from that it was a personal gift from Ferry Porsche to their family member- a key Manager in the early days of PORSCHE.  I promised to keep the family name private, so will not publish it here, but the name is well known.
​Amazingly, it still runs!!
My luggage rack is an original chrome rack in excellent unrestored condition.  Reproduction racks are stainless steel, not chromed.  It also has original straps to hold a ski or ski poles.  There are some nice reproduction straps out there, but the buckles are slightly different.  Racks supplied by the dealer or factory were either Reutter or Lietz.  Amco racks were available in the aftermarket but not dealer or factory installed.
Factory Luggage
The undisputed correct suitcase for a 356C is either a plaid (tartan) suitcase as shown below or one in leather with the same shape and clasps.  I had the plaid one below in my previous car, Miss June, and the car and suitcase are now owned by Bub Mulica.  Photos of it are shown below but carefully note the very special clasp.
At the same time as production of Miss April (1965), 911's were also being produced at the factory and luggage was an option for them as well.  The 911 factory option's for suitcases included both a soft sided suitcase like above, but also a more traditional suitcase shape- No zipper and instead a use of traditional clasps.  Depending on what brochure one ordered from, 1965 an owner could have ordered either type.

Below are photos of the luggage I have.  Suitecase is the "traditional" shape.  

Note on the portfolio and on the soft bag that the clasps are the exactly the same as on the soft-sided suitcase above.  I cannot claim these as factory supplied accessories, but clearly, at a minimum, they were made by the same supplier during the same time period.  
Miss April has a correct Blaupunkt Frankfurt radio and supporting documentation.  Note the correct radio antenna with a blue tip- made by Bosch.  Another very original feature shown below is the splitter that takes one input and then goes to the speaker in each footwell.
Here is a photo of the speaker grills with ORIGINAL speaker cloth.  Nice to have, hard to find, but not quite good enough to keep installed.  I installed a set of reproduction cloth from Peter Silten.  
Thought I'd add a video of how to change the bulb in the Blaupunkt.  Hope this is helpful!!
Below are a couple of photos of Ferry Porsche with his umbrella.  My factory issued umbrella is exactly the same!!!
Although technically not an accessory, a glycerin bottle came in the elastic strip on the inside of the glovebox door as standard equipment.  It was used on the rubber parts to keep them supple and it was recommended to use in the door lock to keep ice from forming inside the lock in terrible weather.  Most were thrown away. 
My bottle is shown below.  Not the prettiest one out there, but it's mine.
 I helped with an article that is published on the 356 Registry website on glove box items.
Here is an article on the 356 Registry site that I helped out with some photos of original key fobs I have owned.  Might help some in determining original vs reproductions