Football Manager 2012

My youngest son keeps playing my Football Manager 2012 and I want to shift him off onto the other PC in the house. I need therefore to get another version of this game on his steam account instead of mine. I can see it online for $30 ish but I know it is frequently 'on special' and I am sure I have seen it as low as $12 in the recent past.

If anybody knows where I could get a Steam key (very lazy, only want to buy online digital download, not interested in going to a shop), it would be much appreciated.