Think the bracelet for these models comes as a kit with everything you need. Tiktox list a braclet for a GW-2000 which IIRC should fit your GW-3500 > http://www.tiktox.com/gw2000bd-bracelet-p-2534.php . It's £95 though. Might be worth contacting tiktox to discuss what you need and what they have...