How do I get \texttt with bold face in LaTeX?

There are the Latin Modern Fonts, from their README:

The fonts are based on Donald E. Knuth's Computer Modern fonts in the PostScript Type 1 format

In family lmtt, there are even three series:

\documentclass{article}
% \usepackage[T1]{fontenc}
\usepackage{lmodern}
\begin{document}
\ttfamily
\fontseries{l}\selectfont light
\fontseries{m}\selectfont medium
\fontseries{b}\selectfont bold
\end{document}

They are also available in OpenType font format with a math version.

The number of glyphs is dramatically increased in comparison to the old Computer Modern fonts.

Thus indeed much has happened in the last twenty years.

I just ran across it and found a simpler answer here: https://en.wikibooks.org/wiki/LaTeX/Fonts

\usepackage{bold-extra}
...
\texttt{TT Text \textbf{Bold TT Text}}

Use Bera Mono:

[...]
\usepackage[T1]{fontenc}
\usepackage{libertine}%% Only as example for the romans/sans fonts
\usepackage[scaled=0.85]{beramono}
[...]
\begin{document}
\texttt{\textbf{foo}}