The latest site recommendation was Smart Madness, they only offer a "Sticker",
to dress up the emblem.
Go to your local Mercedes Benz dealer and ask them to order this emblem for your smart:
Emblem - Smart (451-817-05-16)
The dealer's cost is $34.00,,,,,,when you share this with them they should quote you a very good price.
It should just pop onto the original site,,,,,,although we don't know how you lost the original.