K&N would be best value for money in South Africa,
You can get this at ATS in Randburg, Gauteng. (Not sure about CPT and DBN options) (When purchased mine I paid around R800 (Cannot remember exactly)
http://www.ats-motorsport.co.za/
There are a few Vendors in the US that keep them, but specific vendor shipping costs vary, also consider the import duties etc....Im sure shipping it will cost less than ATS, But if you dont want to wait and deal with the hassle of shipping etc ATS is the way to go...
If anyone else has knowledge of Drop In Filters in SA, please share,
If you going the 'import way':
Here is a screenshot of my personal spreadsheet
filtered for K&N DIF and the Blitz DIF. (These have estimated prices)
(Theres no 'price check' apps for mods 
have to do it manually)
You should check on
www.ebay.com and
www.amazon.com as well
Hope it helps,
