I don't know that I would assume that wooden medal (so to speak) would not be a sacramental. I called my son the priest to ask him before posting this. He said, "I have absolutely no idea. No one has ever asked that before. It seems to me that it should be a sacramental if properly blessed. Something could be a medal without being made of metal." He is going to email his bishop and ask him.
My goodness, I am a lousy typist. Let me try that again.
The bishop did reply. He stressed that this was only an opinion since he had never thought about this exact question before. His Grace said:
"From a Byzantine perspective, I see no problem with this. One could wear a cross made of metal or wood, and it would make no difference. Icons can be painted on wood or canvass or etched in stone or metal. The St. Benedict medal is really a Latin rite matter, however, being as it is associated with a mainly Latin rite order. There may be specific Latin rite regulations about its use or composition. I would suggest contacting a Benedictine monastery and asking their oblate director. He would be the person most likely to have the answer at his fingertips, I think."