Refer to Change your Apple Account country or region - Apple Support
The ideal solution would be to pay for the item. Read the links below about various ways to pay for items in the iTunes and App Stores. Joining a Family Sharing group would be the easiest way given what you describe.
- Add a payment method to your account. See this article about payment methods that you can use with your Apple Account --> Payment methods that you can use with your Apple Account - Apple Support then see this article about how to add a payment method to your Apple Account --> Add a payment method to your Apple Account - Apple Support
- This article outlines how to redeem an Apple Gift Card or App Store & iTunes gift card --> Redeem your Apple Gift Card, App Store Card, or App Store & iTunes Gift Card - Apple Support
- You could also look into joining a Family Sharing group where the family Organizer's payment method is used. To learn how to join a Family Sharing group, read the section "Join a family group" in this support article --> How to set up Family Sharing on your iPhone, iPad, or Mac - Apple Support
If you cannot add a payment method your alternative is to create a new Apple Account when you are in the new country. Avoid doing that if at all possible. It may cause many complications with your current account content.