Using the instructions here at Wikihow, we made our own pH indicator paper.
We used the 'recipe' for eldeberries as we had a stash of them in the freezer. Ds2 defrosted them in the microwave and then crushed them in our metal orange juicer (a potato masher would have done just as well) to get the juice.
We cut up strips of art watercolour paper (acid free) that we happened to have in our cuboard and dipped them in the juice before hanging them outside to dry.
Testing them with lemon juice (acid) and baking powder solution (alkali) produced the following results. Acid = red, alkali = blue/green