Flour – Quinoa Flour Substitute

No, you don't.

Pastry flour is usually low in protein/gluten compared to A/P or bread flour. It may also be more finely ground. Both help in achieving a light, delicate texture when baking cakes, cookies, biscuits, etc.

But it's not necessary. Especially if they're asking for a 3/1 mix, you probably won't even notice the difference. Just be careful not to over-mix the dough: this encourages gluten formation and forces out air, thus resulting in tougher, denser cookies. Letting the dough rest in the fridge or freezer for 20 minutes prior to baking can help avoid this as well.

Alternately, substitute oat flour (grind some oatmeal in a blender / spice mill if you don't have any) - it has no gluten, and will add a pleasant, nutty flavor to the cookies.

I would go out an buy some.

Dough textures for gluten-free breads are fragile and the result of extensive testing with various non-wheat flours (at least, good ones like Serious Eats are). None of the other flours you have available will have the same water absorbsion or starch content which rice flour does. If you substitute, you'd have to make the recipe several times in order to recalibrate it.

Besides, rice flour is generally pretty useful if cooking for someone who can't eat gluten. So you'll use the rest of it. And if you can find it in a bulk foods store, it's quite cheap.