It's a total long shot, and you may have already tried it; however, the names and birth years lead me to suggest looking into Edmond Alonzo Alexander as your Leonard's father.
He was the son of Thomas Alexander and Syrena Emerson and was born in 1864 in Webster County MO. I don't know anything about marriages or migrations, but you might be able to trace him on censuses. The family remained in Webster County at least through 1876 when Thomas died, and some of Edmond Alonzo's half siblings remained in Webster County throughout their lives.
Sorry that I don't know more, but, if this lead checks out, Thomas's descendants (I'm not) may be able to provide more information. Good luck.