One Size Secure the Blur Makeup Magnet Primer is a popular choice among beauty enthusiasts. It is available in several physical and online stores. Here are a few places where you can find it:

1. Sephora: This is the most common place to find One Size products. You can visit their physical stores or shop online. They offer a wide range of products, including the One Size Secure the Blur Makeup Magnet Primer.

2. Ulta Beauty: Ulta is another beauty store that carries One Size products. They have both physical stores and an online platform.

3. Amazon: If you prefer shopping online, Amazon is a convenient option. They often have a variety of One Size products available.

4. One Size Official Website: You can also purchase the primer directly from the One Size official website.

Remember, availability may vary based on your location. It's always a good idea to check the availability of the product on these platforms or call your local store before you go.

Additionally, I would recommend checking the product's ingredients before purchasing. As a skincare expert, I advise you to always make sure the product is suitable for your skin type and doesn't contain any ingredients you may be allergic to.