FWIW the portable URL for the UniProt Mapping service is: http://www.uniprot.org/mapping/. With documentation at:
- Web interface: http://www.uniprot.org/help/mapping, and
- REST service: http://www.uniprot.org/faq/28
The data behind the service is also available for download if you want to have a local copy of all the mappings.
I am not sure if DAVID will be able to map all of them but you can try it. http://david.abcc.ncifcrf.gov/