You can get your symbols from anywhere that suits you...as long as you stick to some basic RULES.. Here are a few ideas.
Remember that the symbols here represent not only the word written alongside them but rather all synonymous ideas, the exact version of which will be clear to you in the context of the speech you are intepreting. So "change" might be "reform" or "alter" depending on the context - you will remember. You don't need a symbol for each word.