The Refuge shop doesn't sell to non-factioners anyway. This is about a lack of Ezrite books in Barovia. But there is a reason for it.
Are the books more common in other areas?
I can understand the notion that Ezrite books are rare in Barovia. But Dementlieu has the printing press and is home to the third sect, who value knowledge greatly. Surely they would have copies to spare? I know the third sect don't actively proselytise, but they do recruit people who come to them, so having spares on hand to give to potential aspirants would not only be sensible but logical.
Also, it's a bit weird that the Refuge shop doesn't sell the First Book to non-factioners, isn't it? As a proseltyizing faith they would surely be handing them out if they could... well, to people who can read.
Not that I mind, I have my copy of the First Book still...