Thanks Tuvok and KR: the shop at the Stanley had the item in store but at an exhorbitant price. The one at Jamia didn't have what I was looking for. I'll try the one in Yaya this weekend.
@ Kularaha, the prices online may be somewhat deceptive in the sense that when you order the lens and have it shipped to Kenya, Customs guys will demand that you pay duty on it. This is likely to result in the overall cost being upto four times as much as what you paid online.
Anyway, c