A good substitute for a nashi pear is an Asian pear. Asian pears are slightly crisper than nashi pears and have a similar sweet-tart flavor. They also have a pleasing crunchy texture that makes them perfect for eating raw or cooking within recipes. Other good substitutes include Bosc pears, Anjou pears, or even green apples if you are looking for something more tart. Whatever you choose, just be sure to adjust the sweetness or tartness of your dish accordingly. Enjoy!