Quite often larger companies will have it uploaded in their Press/Media kit.

These are a few sites that have a large collection of company logos:

https://www.brandsoftheworld.com/
https://worldvectorlogo.com/
https://seeklogo.com

Alternatively it is possible download it straight from the given company's website, using this tool:

https://www.producthunt.com/posts/logo-grabber

Updated on: 15 / 05 / 2020