Because no official book exists, the community has stepped in to fill the gap with fan-made materials that adapt the original Imbued rules to the 20th Anniversary engine:

While there is no core book, there are 20th Anniversary updates for hunter-related content in other books, such as V20: Hunters Hunted II or World of Darkness: Ghost Hunters , available on the Storytellers Vault . Free Community Resources

Here are some steps you could take:

hunters (human organizations like the Arcanum or Inquisition) rather than the supernatural Imbued. World of Darkness: Ghost Hunters

Are you specifically looking for a to run classic Hunter (The Imbued) with V20 rules, or

In 2020, Arkhaven Publications released a 20th Anniversary Edition of Hunter: The Reckoning, which updated the game's mechanics and setting for modern players. This edition included new rules, character options, and scenarios, as well as a comprehensive review of the game's history and development.