Green’s Dictionary of Slang

(US Und.) one who operates (from) an unauthorized office used for gambling and betting on the markets, stocks etc.

1924		G. Henderson Key to Crookdom 254: Bookmakers are closely allied to the bucket shopper in their method of operation.
1930		J. Black ‘A Burglar Looks at Laws and Codes’ in Harper’s Mag. CLX 311: He needs the time to prosecute [...] doctors, lawyers, druggists and bucket shoppers, and the multitude of other offenders who are the by-product of bootleg.