Can anyone send links of Charvaka scriptures in English to either read or download for free onine?
The Brhaspatya sūtras (Lokāyata sutras) are the foundational texts of the nastika Charvaka school. This text has been lost, and is known only from fragmentary quotations. In 1928 published 60 such verses known as Charvaka Sixty and now again published in English.
Shankara discusses this philosophy in his book Sarva Siddhanta Sangraha.
The Sarva Darshana Sangraha written by Sri Madhava Acharya, a pontiff of Sringeri Math in the lineage of Adi Shankara in 1331 AD gives a detailed account of Charvaka, but it doesn't quote Charvaka texts directly, instead paraphrasing the doctrine.
Tattvopaplavasimha is regarded by some authors as belonging to the Cārvāka (Lokāyata) school. But it is disputed by others.
Lokayata: A Study in Ancient Indian Materialism by Debiprasad Chattopadhyaya has some details on this philosophy
The book, Studies on the Carvaka, provides the background of the philosophy and also quotes from extant sources.
In his book A Critical Survey of Indian Philosophy (https://archive.org/details/IndianPhilosophyACriticalSurvey), Chapter 3, Materialism, Prof. Sharma writes:
No original work of this school is extant with the single exception of a much later work, Tattvopaplavasirhna of Jauarashi Bhatta, published by the Oriental Institute of Baroda in 1940. It is therefore very difficult to have a correct idea of it. Our chief resources of information are given on the works of other schools. But this is only done to refute materialism. Thus we often find the tenets of materialism often misrepresented. The weak points of the school are often exaggerated and the strong points are omitted. SO we get only a faint caricature and not a true picture. The Sarva-darshana-sangraha gives a summary of this school, but that too seems to be based on such accounts...But in the absence of the original works, we have to be remain satisfied with these meager and one-sided accounts.