Grab a piece of A4 paper, fold it in half, fold it in half again. Get a pen, draw a line straight down the middle of it and another about 1/2 an inch from the top. Write in this top margin the team names and the captains names (and numbers). Divide each of the halves into 3 and write at the top of each one "T" "C" and "P/DG" Get yourself a stubby pencil you can keep in your pocket and just use tally marks to keep score. You can 'open' the little booklet you have made and keep records of any sinbinnings or send offs. If there is an official card to be filled out, you can always do it later - particularly if it rains you don't want to have the important one in your pocket getting soggy and pencil marks all over it. If you don't already have red and yellow cards, just have a look round the house for coloured paper - no one on the sidelines will be able to tell the difference.
These are pretty good and may give you some ideas about designing your own:
