visit brandreth road lahore, near Lahore railway station.
You can find any sort of industrial, professional and home use equipment and material from there.
This particular product might be available with Longman rubber seals and o-rings store or at least they might be able to help you in searching this particular item.
Dow-Corning is a much better brand if you can get their products that will be best.
However, if you are unable to search it then don't settle for any cheap local or fake product, in that case I will recommend you to buy Harris RTV silicone sealent in black, that's a great product and guaranteed not to leak under the windshield.
You will need 1 full cartridge for the windwhield along with a caulking gun.