You may be barking up the wrong Tree.
I think that the problem here is that servitude, whether indentured, or as a slave, or whether a bondsman, or an apprectiseship was such a commonly accepted practise that it was, to them, a common way of life. Hence the ownership of servitude, in ALL its varied forms, was concidered as being as an intangible right as owning physical property itself.
Would we concider including the right to lets say, owning a car, uncommon enough to include as a right in a "New" Constitution? Well nether did they. That is why they included the 9th Amendment into the Bill of Rights.
No, we would concider owning a car as a understood right of ownership because we had a monatary investment in that property. The same was the practise of servitude in ALL of the colonies and later states.
Even in Massachusetts in 1783, the emancipation of the slaves, under the Quoak Walker case, was an Accident of wording within their State Constitution. And was not appearently to be the intented result of freeing their slaves when the framers wrote that document. They had mearly mimicing the words of Thomas Jefferson in the Declaration of Independence. Who was not, at the time he wrote that document, even talking about abolishing the slave trade. But of abolishing tyrany of a King in England.
In short the thing today that the so called "Slavery Clause" that was placed within the Constitution, and which had to be repealed by the 13th amendment, was placed there strickly for the indulgence of the Southern States, is a false strawdog argument. The "Slavery Clause" has nothing to do with "Slavery". It does not even speak of slavery. It speaks of the right to the ownership of Servitude in all of it legal forms, INCLUDING Persons convicted of crimes.
Article 4, Sec. 2, paragraph 3. use to read
"No Person held to Service or Labour in one State, under the Laws thereof, escaping into another, shall, in Consequence of any Law or Regulation therein, be discharged from such Service or Labour, But shall be delivered up on Claim of the Party to whom such Service or Labour may be due."
As you see the word "Slave" or "slavery" does not appear in that clause of the original Constitution. It appears there only in our minds eye, in that it is what we think we are reading.
Therefore you will probably NOT find direct references to "Slavery" if that is what you are looking for. But you may find plenty of references to property, and ownership of a persons services and labor.