I've got a very basic Skerper one that works well. Looks like you can get one for about £18. I only started using it about a year ago but seems decent enough to me! Gets my knives nice and sharp.
The one I have is 1000 on one side and 3000 on the other. That gets my knives more than sharp enough and it's definitely my technique and lack of experience that prevents them getting any sharper, rather than the stone.
I've got a very basic Skerper one that works well. Looks like you can get one for about £18. I only started using it about a year ago but seems decent enough to me! Gets my knives nice and sharp.