I don't remember exactly where, but I think when I was in the UK I bought a tea towel with an old Irish Blessing on it. It was one that I grew up singing as it was one of my dad's favorites and he would play the guitar at our chapels at the Episcopal school I went to. (Not Episcopal, but my parents worked there.) The tea towel had this printed beautifully on it:
May the road rise up to meet you.
May the wind always be at your back.
May the sun shine warm upon your face,
and rains fall soft upon your fields.
And until we meet again,
May God hold you in the palm of His hand.
Not to get into religion (my background is really complicated!) but especially considering he is going on a mission that might be church-related, this might be a lovely thing to come back with. They are probably everywhere. No matter what one's beliefs, these sentiments are beautiful.
I also agree with everything above: lace, Celtic jewelry, crystal... so lovely! Ele's is my favorite suggestion, though. He can bring that back for me!