How can I fix these chair casters?

There are many ways you can fix casters on a chair or even put caster on a chair that never had any. When I was in the Antique Restoration business I always bought my casters from a company called Vandyke's. Vandyke's also has a online storefront with most of their products offered. I always found the best types of caster to be a two piece system where you have a ferule and post type, this way you can always just pull them out and set them aside when there not needed.