I need a book cover to match a series

I need help with designing a cover to match that of existing books in my travel memoir series. Attached are the existing covers. I like the flag overlay idea but, for this book, there are three destinations: Japan, Australia and Chile. I cannot see a way to get the country outlines on there without looking messy, maybe a world map? I'd love some ideas. I have a strong idea of the colours and images I'd like for the cover (poor quality idea attached) so you need to be able to work with me on this. I only require the art work, as a xcf layered file for use with Gimp, the text will be the same as the existing covers.
Thank you for your consideration. I hope to work with you soon.