What is the history and (current) location of the root text sources comprising the Pali Cannon? Seeking physical and online resources; books; articles; etc. concerning the history, public (and private) images and (current) location of the root text sources comprising the Pali Cannon
Please read the book "The Authenticity of the Early Buddhist Texts" (hard copy can purchased here) by Bhikkhu Sujato and Bhikkhu Brahmali.

The abstract states:


  This work articulates and defends a single thesis: that the Early
  Buddhist Texts originated in the lifetime of the Buddha or a little
  later, because they were, in the main, spoken by the Buddha and his
  contemporary disciples. This is the most simple, natural, and
  reasonable explanation for the evidence.
  
  Our argument covers two main areas:
  1. The grounds for distinguishing the Early Buddhist Texts (EBTs) from later Buddhist literature;
  2. The evidence that the EBTs stem from close to the Buddha’s lifetime, and that they were generally spoken by the historical
  Buddha.
  
  Most academic scholars of Early Buddhism cautiously affirm that it is
  possible that the EBTs contain some authentic sayings of the Buddha.
  We contend that this drastically understates the evidence. A
  sympathetic assessment of relevant evidence shows that it is very
  likely that the bulk of the sayings in the EBTs that are attributed to
  the Buddha were actually spoken by him. It is very unlikely that most
  of these sayings are inauthentic.


Also, "A History of Mindfulness" (and here) by Bhikkhu Sujato (as suggested by Andrei Volkov). 

Another good source is "History of the Buddhist Canon" by Daniel Veidlinger, who teaches Comparative Religion at the California State University.

Also: "On the Very Idea of the Pali Canon" by Steven Collins.

This chapter maybe interesting to you: "Recent Discoveries of Early Buddhist Manuscripts: And Their Implications for the History of Buddhist Texts and Canons" by Richard Salomon.

For a scholarly paper on early manuscripts, see "The Senior Manuscripts: Another Collection of Gandharan Buddhist Scrolls" by Richard Salomon. But this paper discusses only one set of manuscripts that was discovered.

Perhaps, it should be made clear that the oral tradition of the Pali Canon is much more important than the written version. Please see "Pali Oral Literature" by L.S. Cousins. I quote below:


  Early Buddhist literature is an oral literature. Such a  literature is
  not without its own characteristic features. A widespread use of
  mnemonic formulae is one of the most typical of these. I would refer
  to the considerable body of research on the nature of oral epic
  poetry. In such poetry the formulae are used both as an aid to actual
  performance and to maintain the continuity and form of the epic
  tradition.
  
  Both these features are certainly present in the sutta literature. In
  the first place many suttas are clearly designed for chanting. We
  should assume that, then as now, their chanting would produce a great
  deal of religious emotion - the pamojja and piti-somanassa of the
  texts. The difference of course would be that the language of the
  suttas would still be directly comprehensible to the hearers. In these
  circumstances suttas would be chanted by individual monks both for
  edification and for enjoyment. We may compare the recitations
  attributed to Ananda and Upali in accounts of the First Council. In
  practice they would have to be tailored to the needs of the particular
  situation ~ shortened or lengthened as required. An experienced
  chanter would be able to string together many different traditional
  episodes and teachings so as to form a coherent, profound and moving
  composition.