Shopping while on safari is limited. Often lodges and camps have small curio shops where you can buy postcards, local goods such as carvings or books, clothing (hats, shirts), and film. At airports and in larger towns you will find African curio markets where you can by all sorts of carvings, masks, drums, jewelry etc...in general souvenirs and curios are inexpensive (in US dollar terms) - still, fun spirited bartering is the norm.
In most cities there are upmarket jewelers and art galleries where you can easily spend hundreds, even thousands, of dollars on African art. Most reputable shops offer shipping of your purchase at extra cost.