My favorite solution would be to just abolish the Senate and switch the House to a PR-vote with party lists, neatly doing away with all the negatives we have by having a) states and b) districts.
But another fun option would be to just give every state that has a population greater than the median state (
Louisiana) an extra senator per million population over the median state, which would end up giving you:
Louisiana: 0
Alabama: 0
South Carolina: 0
Minnesota: 1
Colorado: 1
Wisconsin: 1
Maryland: 1
Missouri: 1
Indiana: 2
Tennessee: 2
Massachusetts: 2
Arizona: 2
Washington: 3
Virginia: 4
New Jersey: 4
Michigan: 4
North Carolina: 4
Georgia: 5
Ohio: 6
Illinois: 7
Pennsylvania: 7
New York: 14
Florida: 16
Texas: 21
California: 31
68
29
42