You're on the wrong track looking at H1s. The focal length is too long, the filament orientation is wrong (H1 has an axial filament; the Super-Lite's optic needs a transverse filament), and the base won't fit even "kinda sorta". The closest standard bulb is an H3, which has a transverse filament but the focal length is too short and the base flange, while round, is too small. A clever person with the right tools and materials can remove the base flange from a dead Super-Lite bulb and from a 100w H3 and attach it to the H3 bulb's shank, further aft than the H3's original base flange, thus resulting in a very close approximation to the original bulb. The H3's feed terminal is at the end of a short wire instead of directly on the back of the bulb shank, but that's of no consequence; it's the same ¼" male spade terminal.
Start with a 100w H3 from a reputable maker -- Philips, Osram, Narva, or GE. Get the kind with colorless clear glass; forget the "super white" or "xenon white" type of garbage with blue glass. Don't worry about the difference between "85w" and "100w"; both are nominal wattages, and the actual wattage of the original Super-Lite bulb and the 100w H3 are extremely similar.
No, I am not that clever person -- I had it done for me by a colleague some years ago (automotive lighting is my professional field), and the result worked/works perfectly not just by eye, but by lab photometry in my NOS Super-Lite assembly. I was just photographing my Super-Lites yesterday in prep for putting them up for sale. Here are a couple pics of the custom bulb:
I do not know if the guy who built this bulb for me is still alive and equipped.
All the above is if you care about being able to use the lamp as intended (midbeam/turnpike beam). If all you need it to do is light up to show it off at shows and stuff, then you can just apply a Dremel tool to the base of an H3 and it'll fit well enough to light up the lamp, as you can see in
this post.
(Also, be careful out there. I've seen at least one NOS vendor offering ordinary H3 bulbs under p/n 2949241, at eyewatering prices.)
