I don't have links to offer, but I can suggest looking in model railroad products. I needed some thin stripes for a couple of applications (one was the flight deck markings on a 1/1200 Yorktown, another was the border between the silver and white on a Lockheed Constellation), and I got mine from some model railroad suppliers. They were Microscale. Thinner, about 3mm, but you may find something suitable in their catalog.
That's if you've given up on masking the markings. With good tape, like Tamiya tape, you can get crisp borders between the bands.
Where are you in the East Coast? That's a pretty big range I'm in the Mid-Atlantic, in the Lehigh Valley, Bethlehem PA. We have a local club here, the Lehigh Valley Scale Modelers, and the Delaware Valley Scale Modelers aren't far, based in Philly. There's also the Central Jersey club, and New Jersey IPMS, who stage MosquitoCon every year.