http://www.ebay.co.uk/itm/192049104401?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT
A ref recently showed me these and let me have a few, they fit well over a card and basically I just clip my pen on both the card and the match card together so when you need it you have something to write on if you know what I mean. On one side is the essential match stuff, goals, subs, notes etc. other side is team sheet and red and yellow card info.
I've used it a couple of times and it seems really much better than the wallet. I always thought the wallet was a pain especially when you end up trying to get a card out and make yourself look a tit by going to get it out and not being able to.