I just picked up an olivetti lettera 22 at the local goodwill for $5. it has a ribbon but def. needs replacement. i was on a site that sells them in a 3-pack for $24.00. they fit all standard and portables by olivetti apparently. here it is:

http://mytypewriter.com/b53-olivettistandardandportabletypewriter3pack.aspx

Try Office Depot or one of those big box office supply houses.The Lettera 22 is a pretty old typewriter, but the ribbons ought to be available