Brands like Engineered Garments and Rag & Bone pride themselves on their button selection, using contrast colored buttons and genuine vintage buttons to set apart their jackets and shirts. You can do the same, without having to cop a whole new piece. Fabric stores will usually sell buttons, and any capable tailor can sew them into place for a few bucks. Of course, you can also do it yourself for items like shirts too, which will save you more cash.