What type of slot is it? In an IGT S2000, the JKL359xe bulbs can be replaced with certain LED bulbs.. - The florescent bulbs (top box, reel, and belly) can also be changed to LED tubes.., along with the BV light, buttons etc..
Let me know what machine(s) you have, maybe I can help you out.
Picture below is with LEDs installed throughout. (IGT S2000 Double Diamond Deluxe)
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