you will have better luck posting this in the For Sale part of the forum. keep in mind that there are lots of vintage mics that don't "look" vintage at all. you might want to specify what type or post a picture of what you're looking for.
Just get the Shure 55 or whatever the model number is. There's tons floating around (I've seen them a lot at music pawn shops in town) they pretty much define the vintage look and they're fairly cheap.
I helped out a theater group I while back, looking for a simular salution.
Shure 55's look the part, but are expensive props.
There's a couple of companies making look-a-likes for cheap, search under "Elvis microphone", "Retro microphone", "Rock 'n' Roll microphone" etc. Here's an option: