If you are looking for equivalents to the Foundry DA Sikhs (the Brigade Sikhs and KAR are squarely in the WWI period by their equipment and dress), Perry Twins have Sikhs with Snider-Enfields in their Sudan range. They are armed and dressed almost exactly like the Foundry Darkest Africa ones, but the poses are more formal, marching and firing line rather than the skirmish look of the Foundry ones, plus a command set. They are of comparable size, too.
Don't know where else to send you for 1890s British Central/East African Askari other than Foundry, I'm afraid.