It is found in Scripture, both the words and concept.
Nobody comes unless the Father first draws him, and why would the Father draw those who would not come, against His own will? God is not divided against Himself. He has mercy on whom He wills, from beginning to end, salvation belongs to the Lord, and it is entirely of grace and mercy, entirely to the glory of God.
All good questions, and appreciate how you asked them, I sense the friendliness. The freewill debate should be looked at in terms of how it is defined, there is a world of difference between libertarian free will and compatibilitst free will. While it may be said those are philosophical terms, and indeed philosophy is concerned with, and philosophers do attempt at rigid definitions, and work through arguments both for and against, there is value in it, there are things to be learned from them and if all truth is God's truth, we should want to be as close to God's truth as possible, as God allows finite creatures to be. I say all of this because 1.) I once subscribed to libertarian free will, but 2.) I no longer do, because of the Scriptures and harmonizing exactly what you mention "there are verses in the bible that support both views". So compatibilist free will is a view which acknowledges and has a high view of the sovereignty of God and acknowledges "free will" which is defined differently, it is more nuanced, and recognizes the incompatiblism of libertarian free will with reality. If we have to use the phrase "free will", the describer should be limited followed by freedom because to will is nature and all creatures are bound by their nature. To take this even further, God Himself is bound to His nature which is Holy, which is the reason it is impossible for Him to lie, to sin, doing so would be self-contradictory, to go against His own Holy nature. So if God is bound to His nature, it should go without saying that His creatures are likewise bound to theirs. That's a few of my thoughts, let me know what you think.