You're in the right place, though you might get some better advice from the magician (or "illusionist"...whatever) community, though they often want you purchase something to learn the secret. Thirteen Steps to Mentalism by Tony Corinda has an entire chapter on using blindfolds.
The main technique used in cosplay is to stretch (usually black) nylon fabric (like the kind used to make tights) over a frame. You might be able to work up such a rig hiding behind a thin slit in a fabric blindfold, but it wouldn't stand up to scrutiny.
On rigid masks, we use privacy film over clear sheet plastic. One variety is a reflective one-way mirror effect, another is a dark "blind-man shades" effect. I don't think this helps you though.
Elastic or cotton bandages tend to be pretty see-through. Again, under scrutiny, one can tell that the eyes are still visible. Cheesecloth also works. So does burlap, but it's not terribly comfortable. Lighting is important here. The brighter the environment you're working in, the heavier you can obscure your vision.
If you wrap a genuine blindfold poorly, you can get by well enough just by peaking down along your nose. You just gotta know your environment and be careful if trying to walk around.
If you don't mind spending money, you can use video glasses such as Vuzix wrap combined with a small camera. I don't know if there is a wireless model on the market yet, so you'd have to figure out a discrete way to run the wire down your neck. You can build your own wire by soldering the connectors to speaker wire (the thin wire used to make electromagnets) and it'll be barely visible.
Hope this helps!