Hi Aleksander. I will give you 2 options based on cost.
This is a simple combo stone. It's really all you need and it's good:http://www.chefknivestogo.com/imtwosi1kst.html
This 5pc set is cost effective and will give you a low grit stone that comes in handy as well as a couple popular accesories that are useful:http://www.chefknivestogo.com/3pcstoneset.html