Can't really suggest any shop but you may try shahid autos in koh, or other new parts suppliers in saddar area.
New ones will be both cheap in quality and price wise but will serve it's purpose for quite some time at least.
No matter if you find the genuine ones and in good nick as well they tend to tear apart if you commute in area with a lot of speed bumps.
If you found the new ones please update it here also.