An excellent neck lanyard with breakaway feature is made using a shoelace and a short length of plastic tubing. Rather than furnish the link to my prior posting, I'm repeating it here with the addition of pictures:
I virtually all the time wear a neck knife (Benchmade Tether knife). Total weight with lanyard is 61 grams.
When hiking I add a Photon freedom microlight (white or tourquois night vision green). Beyond that I keep things in a pocket with a fine cord lanyard securing some items to belt or pants loop.
The lanyard came with the knife. It is a break-away design consisting of a round, tightly-woven ~5/32" dia. hiking-style 28" shoelace. The ~9/64" dia. ends are pushed into a 1 1/2" length of clear plastic tubing (PVC?) with a 1/8" ID (~7/32 OD). This holds very securely but will quickly come apart if snagged and pulled hard; no danger of choking. The beauty is that if pulled apart nothing breaks; just stick the end back into the tubing. Also, the way I thread the cord through the lanyard (I add the light at the loop on the front of the sheath it is contained), it is very unlikely that any individual item will separate from the lanyard; you won't loose anything (except the whole works over a cliff!).
These are very easy to make. Any desired shoelace will work; just find a piece of plastic tubing (hardware store, hobby shop, etc.) that has an ID that will provide sufficient friction fit to the lace ends and you're in business. I even considered spraying the lace with a DWR treatment to minimize sweat absorption but that really hasn't been much of an issue. It's easy to add items and a longer shoelace would allow the tying of multiple loops to prevent items from all bunching together.