The bulb is "H4" but can be directly used in HS1 sockets.
This is Avenger coil plate which I purchased from one of authorised service center in Thane. MRP is INR532. Its official part name is "Avenger stator plate". The coil plate is direct fit for Avenger (original 180cc engine) and Pulsar 180cc DTS-i fear the black version (and could be for other 180cc models except original 180cc engines)
A neighbourhood mechanic swapped out the coil plates for me for a service charge of INR100. As the part is direct fit, you may be able to do it yourself if you have all the tools.
The light is much brighter now. I haven't taken "before-after" photos though. This upgrade is mainly intended for riding in Pune city than highway riding. Hopefully the stupid pune drivers someday know road manners.
