Combine North and South Dakota into one state and keep the number at 50. Or combine West Virginia and Virginia.
Another alternative -- possibly even more practical than my previous one -- would be to permit New York to divide into New York and Hudson but only if this is paired with the secession of two other states.
The minor benefit to this arrangement is that it reduces the number of states to 49, which would make a neat and symmetrical 7x7 pattern for the stars. The major potential benefit is financial.
There are secession movements active in several states -- and my understanding is that the states most eager to secede are in general the states which take more money from the federal government than they contribute. Since more than two states are interested in seceding, it might be possible to auction off secession rights to the two states willing to pay the most for the privilege. That would mean an immediate short-term reduction in the deficit when the winning bidders pay for their prize followed by a continuing long-term reduction.
Imagine, for instance, a bidding war among Mississippi, Alaska, Alabama, Louisiana, South Carolina and Kentucky. (I don't know if there's sufficient interest in secession yet in New Mexico, West Virginia, or the Dakotas, but if there isn't the Koch brothers might be able to finance a grass roots movement to get them into the auction.)
Some restrictions might need to be put on eligibility for the auction, to keep some states from taking part. Rick Perry in Texas, for instance, has been making secessionist noises; but Texas pays out more than it takes in. Similarly, Massachusetts, New Hampshire, Connecticut and New Jersey should be discouraged from seceding. But those are details that can be worked out later.