I dont think i really trust making one, and buying one will set you back around 2 grand, and that's only with probably one lens, maybe two. I haven't used an adapter yet, but its the next big thing on my shopping list. I've heard they overall a bitch to shoot with though, definitely not something you would typically use for skiing.
I doubt he really requires the shallow DOF, no offense, so i don't think he really requires a 5d mark ii, or a 35mm adapter otherwise.
Maybe he does though.
What exactly are  you going to be shooting?