Rose Family Astringents.
Here come the YARFAs!
You'll find them in all herb books, but very few herb writers know about them. So you'll find a mention of raspberry (Rubus idaeus) leaf being good, as a tea, externally, for sunburn. And the same book will tell you that strawberry (Fragaria) leaf is good for gum trouble, and that avens (Geum) is excellent for diarrhoea.
What this writer missed is that they are all due to the same mildly astringent action - and that action is found in a lot of rose family plants.
If you don't have raspberry leaf use strawberry leaf. If you don't have avens use agrimonia. If you don't have agrimonia use the leaf of rose, apple, peach, blackberry (Rubus), rowan (Sorbus), cinquefoil or other potentillas, spirea, alchemilla, or any other of the large number of mildly astringent rose family plants.
There's lots. There's no need to go find a specific one if you want to calm your diarrhoea or your sunburn: they'll all work. As will all the more or less astringent plants in other plant families; the one astringent you'll find in every kitchen is normal black (or green, or oolong) tea, a Camellia in the Theaceae family.
One caution: there's cyanoglycosides in the rose family. Don't drink too much of that rose family leaf tea if it tastes strongly of bitter almonds. This caution is why I didn't list the leaf of bird cherry, cherry and plum, which are various species of Prunus: I'm too chicken to try the leaf of the Prunuses, and therefore, I have no idea how loaded they are.
Another caution: I don't know if cotoneaster leaf (another rose family genus) is toxic or not. Over here the berry is considered toxic; I don't know if that's true, either.
There are of course rose family plants with other actions: meadowsweet (Filipendula ulmaria) is much more of a painkiller and sweater than it is a simple astringent.
I prefer to save my raspberry and alchemilla leaves for ladies with menstrual troubles.
I love my agrimonia and potentilla for their "give me room" action.
Hawthorn (Crataegus) strengthens both the heart and the capillaries, giving a boost to most (but not all) hearts which need one.
Given a choice (any choice), I don't use those for their astringent action. At all.