Anybody know where I might be able to find this item?

The best bet is to contact the retail people on the links page and to keep a search engine bookmarked on ebay for something to the effect of "5x7 film holder (folmer,graphic,graflex)" I know you know the difference between the phic and the flex, but a lot of estate sale resellers don't. also watch out for graflex PLATE holders, as at best they will be difficult to use if they have the glass plate to film adapter in them, and if that's missing you'll have to resort to wet plate photography or find a good astronomer friend, as they still use glass plates.