A lanyard is a small thing that stops an expensive habit - whistles put in a pocket get lost, and a whistle you have to hunt for is a whistle that arrives too late to be any use to the dog.
Bisley make most of what is here. The cord lanyards come in 3mm, 3.5mm and 4mm with single or double clips, which is the decision that matters: one clip for a single whistle, two if you carry a 210.5 and a 211.5 and want them both to hand without swapping. There is an adjustable 3.5mm in recycled cord, a plaited leather version and a twisted cord with a brass ring for anyone who wants something smarter for a shoot day.
For wildfowling and pigeon work the Illinois River triple call lanyards and the Flextone four-loop in Realtree carry several calls at once and keep them from clattering together, which is the whole point. There is also a retractable Viper key and ID lanyard and a Special Ops retention lanyard, and an Acme 470 clicker supplied on its own lanyard for training.
Related: gundog whistles · ACME · collars and leads · calls and lures