The construction of the 12V/1.2W bike light is identical to the 12V/0.6W light. It simply requires a swap out of the LED bulb. The 12V/1.2W LED bulb uses 10 x individual bright white LED's mounted on a PCB which is secured into a semi silvered glass lense.
The 12V/1.2W LED lamps became available at a reasonable cost about 6 months after the 0.6W LED lamp (click here for details)so i quickly upgraded the original 0.6W light to the 1.2W.
This was fairly simple. All i had to do was solder on power leads to the terminals and then connect them into the terminal block of the rear of the main body.
In this picture i have also shown a 12V/5W LED lamp i purchased a few years later. this was the last i was able to solder power wires to. It was also unusual in that it's body was made of cast aluminium. Very soon after the sources i used had all switched to plastic bodies.
Here the 12V/1.2W light can be seen being bench tested with the 'side looking' LED's clearly visible.
I used this configuration on my bike for over two years.