The green bullet's fine for most of us slugs. I've wowed plenty of crowds playin' through one of those (not meant to be a brag-- just that most crowds are not as picky as harp players).
Harp mics are a funny thing. Almost any mic will get you adequate sound, but mics sound much different through different amps, and so you get favorite matchups for different kinds of sounds.
I've played harp through good vocal mics eq'd for voice & run through the mains and nobody cares that I don't have a customized mic with a vintage element run through a couple effects pedals.
You'll see on harp forums that alotta guys just use Shure SM57's and 58's, right into the mains.
My suggestion is that you contact Greg Heumann at
http://www.blowsmeaway.com harp mics and tell him what you use a mic for and what you want, and he'll build you either a stick mic or a bullet for a little more than twice the small price of a new green bullet. It's not much more money and he's a great guy with the best credentials in the business.