My current CP project is metal.
Come to think of it, I don't have any cabinet that has a wood CP nor have I managed to salvage a cab with wood. Just dumb luck I guess.

Back to the topic. I know there are a few places selling blanks in one fashion or another but I've always found myself doing the work myself. Whether it's patching an existing CP to make fill in errant holes or, like right now, fabricating my own. The dominate panels in my collection are from the "Z back" Dynamos with the fold-down front CP. They ALL need work so I haven't done much with them. The rest are custom interfaces such as Hang-On.
It really comes down to personal preference I guess. My current project is metal because I intend to anodize a color into it. Wood is nice, but it's near impossible to get that look. That's all.