one of the main uses of http basic auth is restricting access to files, so knowing the file path and username doesn't help. As Kulverstukas stated this leaves you with the two options of breaking in, or bruteforcing the password.
Since you don't want to bruteforce, your next steps would be to do a little bit of recon. Theres the chance that there may be a known weakness in the http server that can bypass the basic auth. May be able to use some sort of LFI or abuse bad configuration to obtain the .htpasswd, or perhaps find a way to overwrite that file or .htaccess.
And of course if you manage to root the server than getting the file in question is trivial
Baring brute-force your available options are very broad and situational to the target in question.