Most Numidians from the various ancients ranges will not look much like sub-Saharan Africans. Apart from being commonly depicted in a short-sleeved or sleeveless tunic, they are normally depicted as being at least partially Semitic in origin: curly beard and longish hair in ringlets, but not Negroid features. A couple of manufacturers have been kniown to confuse "Numidian" with "Nubian", with startling results, but they are rare.
Equally rare are Numidians in "archer" poses. The bow played a very minimal role in warfare in the Western Mediterranean in classical times, and that was true among the Amazigh peoples as well. However, because there were a couple of references to "Moorish" archers (in the ancient world, Moors were simply cousins of the Numidians: both Berber, or in their own language, Amazigh), a couple of wargame figure ranges have followed suit.
Moorish archers are available in 28mm from Gripping Beast:
http://grippingbeast.com/product.php?ItemID=1205
...or Navigator, now Magister Militum:
http://www.magistermilitum.com/product.asp?numRecordPosition=8&P_ID=1767&strPageHistory=cat&strKeywords=&SearchFor=&PT_ID=1275
...but as you can see, these aren't exactly the sort of fellows you'd have beenlikely to encounter along the Congo in the 1880s.
An option for spearmen might be Gripping Beast's "Desert Frontier" native spearmen in loincloth (the ones in teh upper half of the photo):
http://grippingbeast.com/product.php?ItemID=145
I have used these for various Nilotic/Sudanese tribes. But the oses aren't really suitable for archers, especially as (in common GB practice), the shield hand is a bit of a nub, and would reguire re-sculpting to hold a bow.
Sorry I can't offer any better suggestions (I just sucked it up, and have lots of Foundry DA archers--and pygmies!). But I wanted to let you see what Numidians looked like before you headed too far down that path.
One last thought. 1st Corps makes a pack of "Numidian Skirmishers" (PU25), which are inexplicably sculpted with Negroid features, and have elaborately coiffed ringlets:

They are quite small, almost "true 25mm", and as you can see, the poses are going to make conversion to archers difficult.
Allen