Yeah, eBay has some vendors selling used ESS goggles, like these:
http://www.ebay.ca/itm/ESS-PROFILE-S...#ht_924wt_1397
Make sure they're the NV profile, as hectic said to aim down your sights/optic. Now you can also get a version with a fan preinstalled for a premium price, assemble your own fan, or use defogging agents. I recommend getting a fan if you sweat, because the goggles will trap the heat in it will get sweaty and irritating.