If you are making it for later, add the shredded potato to cold water, rinse and pat dry well before adding to other ingredients. This way potato won't change its color.
You can use zucchini, pumpkin to name a few.
If you don't have any ingredient handy (like sweet potato), substitute equal amount of any other ingredient.
For egg substitution use rice flour or corn starch. Please refer potato tiki recipe for the quantity of flour.
Try to flatten it as thin as possible. This yields a more crispy texture.