These sources can be St. Bernard himself and/or any individuals that have ties/ relationships with the Knights Templars. The time period must be 1100-1200.
Many of his works are easily accessible online or on Amazon. If memory serves his collected works are available in a Kindle edition for just a few dollars. Life and Works of Saint Bernard will be a good starting point, some of his other works such as his sermons and letters may be of use. You may also want to look at the Council of Troyes and associated primary sources as well as Clairvaux's work In Praise of the New Priesthood which discusses the Knights Templar in particular. He wrote in Latin but English translations are widely available.
Don't know if you have tried archive.org, but might be some material you could use. None directly primary sources, but might be some direct quotes from original documents.
Review the bibliography for the text "Holy Blood, Holy Grail". There is quite a list present. Also try corresponding with the author named Lincoln. He may be the only one yet alive. They did extensive research on the Templars and could potentially add a great deal of data. Good luck!
St. Bernard of Clairvaux : the story of his life as recorded in the Vita prima Bernardi by certain of his contemporaries, William of St. Thierry...[et al.] / a first translation into English by Geoffrey Webb and Adrian Walker.
Other Entries:William, of Saint-Thierry, Abbot of Saint-Thierry, approximately 1085-1148?
Webb, Geoffrey.
Walker, Adrian.
Published:London : A. R. Mowbray, [1960]
Description:130p : port ; 19cm.
Subjects:Bernard, of Clairvaux, Saint, 1090 or 1091-1153.
Internet History Sourcebooks Project. at sourcebooks.fordham.edu is a good site for primary sources for Bernard of Clairvaux and Knights Templar. Also check out William of Tyre's History of Deeds Done Beyond the Sea for primary source of Knights Templar
The books 182 to 185 of the Patrologia Latina are dedicated to Bernard of Clairvaux's writings, it could be a useful source for you. You could also find elements in the biography by Pierre Augé : Saint Bernard de Clairvaux, Paris, Fayard, 2003.
The bibliography of Jochen Schenk's Templar families: landowning families and the Order of the Temple in France, c.1120-1307 might also be useful to you. Schenk's work focuses on how the Templars cultivated multifaceted social relationships, so I would think that it would be useful in addressing the second part of your question. If you're looking for more on the response of ecclesiastical and/or religious figures to the Templars, I'd recommend the indexes of e.g. Mansi (Amplissima coll. conc.) or Canivez' Statuta, for the Cistercians' General Chapters. Depending on what geographical area you're focusing on, the MGH might also be useful.