Verity’s Ultraseek, a search engine, is now available for download and free trial. This is the tool we used at ASHA when I was working there. Excellent ability to tune results and the interface can be customized relatively easily using Python and HTML (although the templates were rather incomprehensible spaghetti code, which is hard to do with Python, normally). Hopefully the spaghetti issue was improved with the latest release.
Spotted via SearchTools.