It may happen that a seller may mistakenly have missed out an item from your bundle, if so we would first always recommend you get in touch with the seller to let them know and give them a chance to resolve it.
If you aren't able to come to a resolution then we would advise you open a PayPal dispute here Make sure to open a dispute for an item that is not as described.
As you have received part of your bundle, we advise a ‘not as described’ case as it’s incomplete and you are better able to resolve it. For example, the seller can offer to partially refund any missing items.