I'm not sure about your exact typewriter, but about 95% of typewriters use a standard 1/2 inch ribbon, there are many places that sell them online, a reliable one is shown below.
The Underwood 1 typewriter, introduced in 1895, is considered the first modern typewriter due to its innovative design features, like the familiar QWERTY layout, shift key mechanism, and automatic ribbon reverse. Its success helped establish standards that influenced typewriter design for many years to come.
Underwood Typewriter Company was created in 1895.
The typewriter ribbon is the store of ink for the typewriter. When a typewriter key is pushed the letter springs up and hits the ribbon - pushing the ink onto the page in the shape of the letter.
How do you change the typewriter ribbon of a Smith Corona 1940?
The best site to purchase Smith Corona typewriter ribbon (considering price and reliability) is via Ebay. The typewriter ribbon can also be bought on TigerDirect.
Underwood
A typewriter ribbon can be found at many places in stores as well as online. One place that sells typewriter ribbons online and in stores is Office-depot.
www.FJAproducts.com has just about every typewriter ribbon, Time Clock Ribbon and Cash Register ribbon ever made. Flat rate shipping of 4.95. Toll free in the USA 800-982-9989
There are lot of types of typewriter ribbons present in the patent database.
Product ID: BR277 universal ribbon
Some words you can use with "typewriter" are keyboard, ribbon, keys, and vintage.