How do you disable the seatbelt reminder?

You might be able to find a fuse that this is somehow linked to, but now adays manufacturers are making it harder and harder to turn these safety features off. I hope you find your answer.

You may have to cut some wires. A Haynes manual will show you a wiring diagram which should make it easier to find the chime unit and disconnect it. These are typically removable from the older vehicles -- you have posted twice, once as a 1994 and once as a 2004, which are vastly different. You may also want to try getting a factory shop manual on Ebay, which will tell you how to do this also.