what do you currently use to grate wasabi besides sharkskin
Second best to shark skin is a good hand-made metal oroshigane, most of which are made out of copper. They are much sharper than the ceramic ones. Some sushi chefs, including Jiro-San prefer these to the shark skin graters. There are aluminum ones that are cheaper, but one of the hand made ones is something that will last you decades. Korin has a nice copper one and a heavy duty aluminum one if the copper is out of your budget.