I have had good luck with Baco 314 835 9300. Not on web or email. Most Teletype take standard Underwood ribbons

You want all black. Nylon is the longest lasting and sharpest bou cotton prints darker. You probably want eyelets for the automatic reverse. If the spools are special it's easy to wind the new ribbon onto the old spools. She may have the violet color used on some press Teletype. Don't remember the prices but they are reasonable. She has probably supplied replacements for machines like yours and knows the specs. Just ask.