You can use the Supreme toilet it is designed for banjo counter tops.
MS863113-01 1.6 gpf Regualr rim toilet 1pc with soft close seat 23-1/2" high.
MS864114-01 1.6 gpf Elongated rim toilet 1pc with soft close seat 23-1/2" high.
or you can use the 1.28gpf which is the same codes except it has an "E" on the end.
and if you need handicapped high you can use
MS864114L-01 1.6gpf Elongated rim ADA with soft close seat 25-1/2" high.