Yes, you can purchase the add-ons separately. Here are the links for the upgrades: Niches (100 Niches Upgrade), PDF Templates (15 PDF Templates Upgrade), and DFY Pack (DFY Pack Upgrade).
Make sure to use the same email address you registered with, so all upgrades are seamlessly added to your account. This ensures you have uninterrupted access to all your purchased materials in one place.