Some scholars estimate that only 25-30% of all Scottish surnames have a connection to Highland clan, so in reality, your friend would in some ways do better to join a St. Andrew's/Caledonian Society. Some (but not all) of these societies have "open" memberships in that anyone with an interest in Scotland may join as members.

For those who choose that route, the district tartan is always an option, be it a national, provincial, state or another form of universal tartan, such as the Caledonia tartan.

Yours aye,

Todd