Based on this product's specifications, here are some alternatives and similar models
Protective Adjustable A4 Book Cover Narnia model 13 — pack of 50, reusable transparent covers
Summary description:
Adjustable A4 book covers Narnia model 13 are transparent protective covers sold in a pack of 50. Designed for A4-format books and notebooks, each cover is adjustable to fit varying spine widths and protects against dirt, moisture and wear. Suitable for schools, offices and home use to preserve textbooks, workbooks and documents.