Franco Library at Alvernia University, which houses The John Updike Society Archive (renamed, apparently, John Updike Collection), has catalogued the holdings digitally and made them available online so scholars and researchers can see the full range of items in the collection and decide whether there are materials that might be of use/interest.
In fact, archivist Gene Mitchell says that if any Society members email him to set up an appointment while they’re in Reading to attend The Third Biennial John Updike Society Conference, he will make arrangements to have those materials ready and waiting.
Here’s the link to the John Updike Collection.