dealer's band noun an elastic band used by a drug dealer to secure or to facilitate the jetisoning of drugs for sale US
Many addicts–especially pushers–wear a rubber band on their wrists (a dealer’s band, some call it) which, if hooked properly around a deck of heroin, will send it flying if an approaching detective is spotted. — James Mills, ThePanicinNeedlePark, p. 15, 1966