I found this ribbon on Amazon from FJA Products (who make typewriter ribbons):
https://www.amazon.com/Smith-Corona-Vintage-Spools-Ribbon/dp/B00ZMJK67Q

I'm not an expert on ribbons, but they look to be the same design as the ribbons you have. I might wait for others to reply to this topic though, to double check. Hope this helps!
 

Hi Gferdon

If you still have both spools as pictured for your typewriter, simply wind any ½" ribbon onto your spools. These LC Smith typewriters have a proprietry drive system for the spools and regular universal 2" spools will not work on these machines. The spool you have pictured was used on many of the Smith-Corona desk-top and office machines right through until the 1960's and possibly later. Hope this points you in the right direction,

Sky

The spools we get today are plastic and are just pennies of the total price of a ribbon.

If you think about it, you'd want an inked ribbon to come on a spool anyway, even if you weren't going to use it.  Any other method of delivery would make a royal mess. 

Geoff,

I eventually secured metal spools for all of the machines in my collection.  I think they are more robust and more precise than the "universal" plastic spools that most seller offer.  Plastic ones can "wobble" on your machine, in use.  I use 2-color ribbons and with plastic i did get  a bleeding of one color into the next.  Not so with metal spools meant for a particular machine.

Re-spooling a new ribbon from a plastic spool to metal spools on a machine only takes a couple of extra minutes.

Ribbons Unlimited sells 1/2" wide ribbon (in a variety of ribbon fabrics) that are a full 18 yards in length.

Many Amazon sellers and others on line sell spools of ribbon with only 8-10 yards.  So if you are price comparing...you need to find out the length of ribbons offered to see if a deal is really a deal.