Tamar Myers is probably better known for her Pennsylvania Dutch and Den of Antiquity series, but in the late 2000s/early 2010s, she also authored a short four-book series set in the Belgian Congo in the 1950s. The Headhunter’s Daughter is the second book in that series and it has dropped to $0.99 in the US right now.
The Headhunter’s Daughter is $0.99 in the US again right now. The links in the OP just above are still good…
The Boy Who Stole the Leopard’s Spots is the third in this series. It’s $0.99 right now in the US.
Kindle US: https://www.amazon.com/dp/B006FO86CY
Kobo US: https://www.kobo.com/us/en/ebook/the-boy-who-stole-the-leopard-s-spots