In your shoes, I wouldn't bother with that friend you described. Some people don't know how magnets work, some can't play RPGs for lack of imagination. But if you find it absolutely necessary, you could challenge his gamerhood and/or manhood by promising him a game he can't beat.
However, you could post an add in the school paper or whatever means you have.
However, you could post an add in the school paper or whatever means you have.