Let it buzz for a bit and find where its at, then either a) put tape over it to quiet it down or b) snip the power wires. I'm guessing its fairly well hidden up under the dash. I'm pretty sure its on the drivers side as well.
I put "seat belt alarm" in the SEARCH box and got three pages worth of hits. Just looked for a result in the right sub forum and there it was (page one).
I've done this DIY - works great. You'll still have a short reminder beep for a few seconds, then no more. Good luck and enjoy your 3-4 months of summer!