How about a /Coat of Flame/? That needs a Rego requisite, though.
Normally I don't wear gaming gear, but this is to sweet. I'm going to pass the link on to my boyz.
How about a T-shirt with a small Ars Magica logo on the front and the ArM5 rulebook's cover art (the twelve Founders and the four realms) on the back? I'd buy one in a heartbeat.