On that NPC map…it’s a number of years old. Panhellenic alumnae groups are only as active as their volunteers, which means they wax and wane. If there is no direct link to a website, or if the link goes to a “not found,” try searching for the group on Goggle. Type in “Town Name Panhellenic”. Lots of these groups have abandoned websites for Facebook pages. There are also non-NPC alumnae panhellenics - not registered with NPC but organized to help with recs.
Vermont and New England just doesn’t have many alumnae groups - either Panhellenic or associated with particular sororities. But do try to get the recs you can. You should be able to find a majority of the 15 sororities that participate in formal recruitment. Maybe not all, but at least 7 or 8 of them.