You could get a DMT EF or a spyderco ceramic, or any number of sharpening tools, but what's your goal? Diamonds will provide a toothy edge and a ceramic will smooth it out providing very fine sharpness.
It's always good to ask yourself before a sharpening gear purchase: will this compliment my current gear and needs and will I be able to expand on this in the future. Sometimes a gear purchase can set you back on future add-on's.