Each phone has it's own unique code. If you're a customer in good standing with Verizon for at least 6 months they should provide the unlock code for your device for free. Just explain that you're traveling overseas and want to use a local pre-paid SIM while you're there.
There are paid unlocking services at varying prices. I personally have great luck with Horizon Wireless Online. They charge between $20 and $25 a pop. There are cheaper alternatives but they are often scams. And remember - if you enter the wrong code 10 times then the phone is locked forever to the original carrier.