That's a good suggestion and thanks for the specific recommendation. One challenge I have is that I'm not handy at all, so conducting my own repairs always carries with it the risk of making matters worse!
Still, I'm impatient, so last night I tried to repair with super glue (cyanoacrylate esters). It seemed relatively sturdy after I let it set for five minutes but then the piece broke back off while I was inserting it into the assembly - which is an intentionally tight fit.
This morning I tried a version of loctite that uses a different chemical. I will let this one cure for 24 hours before trying to insert it into the assembly. Both the superglue and the loctite list some types of plastics for which they are not effective but I don't know enough about plastic to categorize these title pages. If the loctite fails, I will try the epoxy, per your suggestion.
A couple of notes:
* Although this piece isn't load bearing, it does take on a nontrivial amount of torque from the gimmal used for flipping pages.
* The numbers seem not to be on the plastic pages themselves; they seem to be stickers. Thus, if I replaced the page, I could try removing the stickers and adding them to the new page or finding replacement stickers, or creating substitute stickers.