Green’s Dictionary of Slang

(US) to adapt, to alter the function, typically of an electronic component.

1959		W. Burroughs Naked Lunch (1968) 100: He fix up two ropes — one gimmicked to stretch, the other the real McCoy.
1963		A.S. Fleischman Venetian Blonde (2006) 185: The book [...] was nicely gimmicked. Pages had been hollowed out and a transistor receiving set installed. [Ibid.] 208: The candle had been gimmicked with a short, faked wick to burn out within minutes.