Reply to u/eJelly at https://old.reddit.com/r/typewriters/comments/1kyf66p/ribbon_replacements_for_smith_corona_corsair/
Typically Corsair spools are 1 5/8" in diameter and sometimes listed as 1 2/3" in diameter. Ribbons Unlimited carries them if you need both the spools AND the ribbon: https://www.ribbonsunlimited.com/category-s/12685.htm
Otherwise, if you have spools that already fit, then just buy the ribbon and spool it onto your empty spools to save the $10-15 for the extra spools. See: https://site.xavier.edu/polt/typewriters/tw-faq.html#q1
The eyelets are for doing the ribbon auto-reverse on Smith-Corona machines, but your print will go faint when you reach the end and you can do the reverse manually if necessary.
As a pending birthday stop-gap, I have done the trick before of typing on a blank sheet with a carbon paper and a second sheet behind it. You won't be able to easily see what is on the first sheet, but you'll have the carbon copy behind it!
If you're in a bind, many of the big-box office supply stores carry 1/2 inch wide ribbon for calculators which you could spool into your existing typewriter spools as well. Typically these are much shorter in length, but they'll work in a pinch.