Why not use a split rinmg ... type used as key rings ... when I played about with the boys in Green, the pull ring from an L2 fragmentation grenade used to a popular item for repairing zips.
Consider plaiting a leather or nylon thin rope ... plastic version is popular with kids at the moment ... used to be called Scoobydo when I was a kid, don't know what it is called now.
On a large canvas holdall I use for diving kit ... I used a thin 3 ply rope and spliced it on ... i.e. formed an eye-splice though a key ring split ring and fitted that.