There are about 20 shops in Karachi plaza market (chaat gali) selling teikoku piston ring brand, I dont think it will be easy to find for a 5SFE as this engine was never imported for use into Pakistan.
There is also a cofap piston/ring shop opposite plaza - they also have a huge variety - the Kolbenschmidt piston and ring importer is right next to the SKF bearing shop near Gul Center - they can also look up and quote you the price for it.