Yeah,yeah,yeah. Got back to bed its pass your bed time.
The op wanted to know "positive 12v headlamp source". "Headlight source." So where else would you get it? Your butthole?
Or the headlight switch?
As for dimmers, theres more than one place to get them. Its a violet or purple wire. Can be found I.E... the foglight harness,Window de-icer harness,headlight leveler, and radio but its a pita...