They definitely have the CSL replicas at Hurry Tyre along Bukit Timah Rd, and at Autovox (who are now at Lok Yang Way). I have also seen the Taiwan version (it's a different colour, darker and more polished look) at Leong Seng at Ubi.
They cost about $350 per wheel for the Italian made ones, and about $280 per wheel for the Taiwan ones. The tyres are quite expensive tho, altho' if you are fine with Advan Neovas, or Pirelli P Dragons, you may be able to get the 225/40-18 tyres at S$250 per piece. Any cheaper will have to depend on your bargaining skills and "connections" (if any)....
All in, you are looking at paying between $2,300-2,400. :|