Even though there are single flips, there is a flap that goes over them to fit in an area to secure the flip. The single flips simply don't have two pockets. They are more expensive and if you want to look at the coin in the flip it leaves a partial ring over the coin: Your choice. I think these are thinner than two pockets together so maybe that would work for you.
Once again, look for Mylar, Polyester or PET and for the wording unplasticized or plasticizer free. Wizard Coin Supply is a highly reputable vendor.
I have never tried them. Just looking on the web for alternatives. Also I don't know if the outer measurement allows them to fit easily into coin pockets in a book.