What you'll find generally are mobile and other non-fixed furniture style kitchen islands, as well as a few fixed-in-place islands. Costs for small kitchen islands are substantially lower, due to the fact that fewer quantities of high-priced materials (granite, solid surface, marble, etc.) are being used. Also, most of these small kitchen islands are easy, DIY assembly projects.
Compare Prices: Edenton Kitchen Island by Home StylesShown here is a small kitchen island from Edenton Kitchen Island by Home Styles. At 48" long by 25" deep, this is as close to a "real kitchen island" you will get in a small kitchen.
This island can either be left unfixed on the kitchen floor, for moving to other spots at a later time, or can be fixed in place with just a few screws.