Here's the U.S. disclosure site: https://lda.senate.gov/filings/public/filing/search/

I've been working on building an improved version of that site (allowing users to search by the issue being lobbied on, show trends by company, etc.) but it's still in the pretty early stages of development. Have a big update coming in the next few weeks though: https://www.quiverquant.com/lobbyingsearch/

OpenSecrets also does great work summarizing lobbying data: https://www.opensecrets.org/federal-lobbying