Contact
http://www.ag-photographic.co.uk/tri-x-400asa-58-c.asp
Ask them to import it for you. If you really want more then a couple of boxes I think they will help you out.
If they do supply you get back with us so that we know this method works.
Also let them know up front that you plan to do this and they might see more sales in the future as a result.