Yes! Just multiply your pledge (not including shipping) by the number of additional patches or sets you'd like. You'll be able add these to your reward as part of the backer fulfillment survey process.
All international backers will have their reward listed at the amount of the reward pledge on the customs form of the shipping label. For example, if your reward is for the $21 3-pack, the customs form will list that description and amount.
Most likely you will be responsible for customs fees when you pick up your package. If you have any questions at all, please contact me or contact your local post office for clarification.
Don't see the answer to your question? Ask the project creator directly.