Hello
The magnetic bracelets used in that study were: "Standard neodymium magnets set in a steel backing cup, with the open side facing the ventral wrist, creating a fluctuating magnetic pattern across the bracelet. The field strength at the wrist contact surface was 170-200 mTesla." Be careful about buying one, there are many such devices on the market and some of them are of dubious quality. You could perhaps contact the corresponding author of that study as he may be able to advise you on purchasing the bracelets used in the study:
timharlow@eclipse.co.uk