Sola Scriptura does NOT teach that something must be found in the Bible to be true or "good". Rather, it teaches that the sole earthly authority for Christians is the Bible. Therefore, if it is in the Bible, then it is true. If it is not in the Bible, then it might be true or not true. If it contradicts the Bible, then it is definitely NOT true. I fully grant that interpretation of the Bible plays a huge role in how this doctrine is implemented, but my view is that is not the doctrine's fault.
For example, you make the sign of the cross on your chest. This is nowhere in the Bible. However, it also does not contradict the Bible, so it does not violate Sola Scriptura. The same can be said about my altar call. Problems arise in such cases as the Marian doctrines, in which case we assert that there is a direct contradiction in scripture. That is the deal killer, NOT that it is simply an Apostolic belief. I think that if many Apostolics could parse the doctrine down to its barest bones, that many could find "some" sympathy with it.
Clearly, since the doctrine was promulgated by Reformers certain assumptions are made. However, my personal view is that the interpretive assumptions are not proving as to the validity of the doctrine itself. IOW, I would much rather hear an Apostolic say: "All of my truly core beliefs via Apostolic interpretation are found in the Bible, and here's where they are ..." (Sola Scriptura). This is as opposed to: "Many of my core beliefs are found in the Bible, and some other core beliefs are found in extra-scriptural Tradition, and here's where they are...".
So why isn't in the Bible. Why didn't any of the early Church fathers write about it, or even later with Augustine and Aquinas.
The fact is that Martin Luther invented it in the early 16th Century as a reason to leave the Church. Even he didn't pretend to have Biblical justification of it. He took advantage of the fact that his "audience" was other excommunicated clergy who wouldn't question him and a populace that was generally illiterate and didn't know if it was scriptural or not.
As has been demonstrated ad nauseum on this and other threads, no Marian beliefs contradict the Bible as long as one is open-minded enough to listen to the Church's theology behind these beliefs.
The bottom line is that "sola scriptura" is a recently invented unbiblical belief that the Church has categorically rejected since the theory was first introduced.
There is a contradiction with a particular interrpetation of the Bible, the one you happen to favor, not with the Bible itself.