How can I insert by .bib file into my .tex file?

You can use the filecontents package to insert the contents of your bib file into your tex file.

Here is an MWE of how it would look using biblatex and bibtex.

\documentclass{article}
\usepackage{filecontents}

\begin{filecontents}{jobname.bib}
@book{author_book,
title = {Book's title},
author = {Author, Some},
location = {The City},
publisher = {Publisher},
date = {2005},
}
\end{filecontents}

\usepackage[style=authoryear,backend=bibtex]{biblatex} %backend tells biblatex what you will be using to process the bibliography file
\addbibresource{jobname.bib}

\begin{document}
\nocite{*}
\printbibliography
\end{document}

Here is a MWE without using biblatex:

\documentclass{article}
\usepackage{filecontents}

\begin{filecontents}{jobname.bib}
@book{author_book,
title = {Book's title},
author = {Author, Some},
location = {The City},
publisher = {Publisher},
year = {2005},
}
\end{filecontents}

\begin{document}
\nocite{*}

\bibliographystyle{abbrv}
\bibliography{jobname}

\end{document}

When you compile this the first time, a bib file is created just like several other files are created (aux, toc, log, etc) so it shouldn't be a problem for whoever is requesting to have everything in a single file. After the first compile, you need to run bibtex as you normally would. Everything is pretty much the same.

Edit: I see now that using filecontents is the solution in the post to which @N.N. pointed in his comment.

After you run bibtex, you can copy the contents of the .bbl file into your document.