A note that there are many different types of "Night
Vision Goggles" and most of them are not binocular, but monocular.
There are "one eye" versions common to snipers, and monocular versions that go to both eyes which are common to
foot soldiers (usually flip down on an attachment to the helmet). Then there are of course the bulkier binocular versions. There are even some with three inputs!
http://www.infrarednightvisiongoggles.com/
This site shows a lot of them.
The real question is, does the actor have to actually be able to see though them, or is there another solution? Or does these goggles never get used and therefore can be a "sculpture"?
To make a functioning
unit, I'd probably take apart a really cheap gun-scope (you can get one for like $10 at the right surplus place, you just need a small one) and pop out the lenses (doubt you want magnification) and
build the prop around the scope perhaps?
Of course I am not a prop-maker, but I know a number of them. *sigh*
props class was fun sometimes though.