Most economical way to get a kosher mezuzah?

Greetings folks.

I’m a student who recently moved to my own place and i want to start keeping the mitzvah of mezuzah. Given that I don’t have much of an income at the moment I’m having to do this on a bit of a budget. Where/how is the best (affordable) way to get a kosher mezuzah and scroll?

If it’s any help I live in South Africa.

Thanks all in advance.