If you are looking for a specific type of text, for example "persuasive writing" you can Google:
"librarythings: persuasive" or "librarythings: persuasive writing" This will take you to crowd-sourced tagged lists of books that are tagged as persuasive writing examples. If you're logged into LibraryThings.com with our school library password (see password document) all our books will have a green tick for an exact match and a grey tick for a partial match (i.e it may be a different edition). We try to regularly update and upload our catalog.
Many schools have libguides with information, including mentor texts. Once again you can just Google: "libguides: mentor texts" and you will get a result of the libguides of other schools who use mentor texts. In particular UWCSEA East has many good guides in this respect.
Most schools operate and "open" catalog in that you can freely search their catalogs for items. If you put "mentor text" in the search bar you can then see all the books tagged as Mentor Texts and then further refine by clicking on the book title and seeing how it has been tagged. Here are a few catalogs in Asia that may be helpful: