This is a highly ill - eagle act to do. In the old days we would put an electric drill on the drive cable, but now they make them tamper proof so they only go one way. The bezels are crimped on so you can't get inside them. I expect modern one may be electronic. How will your insurance company know what mileage you have done? I have never known an insurance cancel or fine due to mileage. You should have just disconnected it when you got close to the limit.
Buy a used one and use them for 6 months in turns. There are two or three here 23K and one with 36k
https://www.google.com/search?q=2002+yamaha+sr125+speedometer
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