That'll do the job just fine. Also, you can buy any manner of Euro-style Vespa headlights with all this gear as well.
You're obviously a stickler for an original equipment restoration and that is totally fine. That level of authenticity is typically only important to collectors. Someone who wants a Grande to ride around isn't going to care whether the headlight is the exact model/make of the one that came on the bike originally, they only care that it works.