Members of both houses of Congress shall be in their respective state and widely accessible to Constituents during 80% of the legislative calendar.
In the 21st Century with current technology they already have the ability to conduct business remotely.
This would make lobbying easier for Citizens and much harder and more expensive for professional lobbyists. Additionally, Citizens would have greater visibility of who the legislators are meeting with.
Obviously, the 80% is up for debate.
I presume some House & Senate rules would need to be modified.
Unfortunately, this might require an Amendment to the Constitution.