I think Vonage has discontinued this item. If you do get a hold of it you can use it in place of your vonage adapter. Just remember you can only have one device per account in use at a time.
A free alternative is Vonage Talk, use a laptop with internet connection, head set and microphone (or built in) when you travel.
http://alpha.vonage.com
Just a note this will take you to the Alpha Vonage site which means all these products are free to use, but are in a trial state, no phone support for them.
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