A pocket square is an essential part of any fancy man's attire. They're also quite expensive for such a small piece of fabric. Instead, make your own with a cheap piece of fabric and some hem tape.
As lifestyle blog The Art of Manliness explains, pocket squares are largely decorative and don't require any major seams. Therefore, it's super easy to make your own. Simply cut the fabric of your choice to size, cut the corners, fold in the edges and apply hem tape to keep the edges clean. You can check out the full instructions at the source link below.
DIY Pocket Square (No Sewing Required!) [The Art of Manliness]