Many public libraries have collections of "holiday" books. Some libraries have them together in one place and other libraries put a holiday sticker on them and keep them with the rest of the books. Parents looking for these seasonal books will find that they are mostly picture books though there are titles for older children as well.
Timing is important when looking for holiday books. Halloween is very popular and there are many titles available so it shouldn't be too difficult to find something. However, far less is written about Columbus Day so you may be disappointed if you wait until October 11. Teachers and others who need a book for a specific date should try to get the book as early as possible. However, keep in mind that sometimes these books may not be taken out for as long as other books. Some libraries do this so that the books are available to more people during the "holiday" season. Some libraries may not let you extend your loan period for this reason as well.
One of my favorite Halloween books to read aloud is Big Pumpkin by Erica Silverman which is available in paperback if you can't find it at your local library.