At hankyu men you can choose the finishing (brass / nickel) as well as the shape (half moon or trapezoid? If your shoes have a squarish welt)
FYI they also do custom laces (flat, round, in so many colors, with brassed tips) - so might want to check that out as well.
Oh and if you're in the market for custom belts - they do that too, in the same place where you would bring your shoes for the metal toe tips. You get to choose the buckle, leather, etc