What's wrong with Gopher? It's a great fit for old machines, and still a very easy way to set up a simple file server.

Anyway, for Firefox/TenFourFox/SeaMonkey, https://addons.mozilla.org/en-US/firefox/addon/overbiteff/ (as mentioned, I'm the author), or for Chrome, Android, iOS, J2ME, etc., see http://gopher.floodgap.com/overbite/ (yes, HTTP).