Even the most recently produced high end forks in 1" are probably vintage at this point. Marzocchi made the marathon or something like that well into the 2000's in 1", but best case that's still a 10+ year old fork. Can't recall the travel on those off hand, maybe 80mm?

Rock shox SID forks are sought after in 1", probably the best combination of short travel/light and available in 1". I think that era of SID forks could be adjusted internally for travel with spacers. The last guy that rebuilt old Rockshox forks is gone now though.

If you can find a Marzocchi with a bolt in steerer you can swap for a 1" tube, actually you can use any older fork but need a huge press if it's not bolted together. Bolt in steerer forks are pretty early, '96-'99 I think. Have not used him myself but there is a guy called Marzocchi Mark, rebuilds them, could swap a steerer for you or probably sell you complete fork.

As far as the fork length, you could probably track down the intended fork length. Retrobike.co.uk is good for that sort of thing, a much more mountain bike leaning classic and vintage forum. Mostly the issue with longer forks is the bottom bracket gets pretty high up there, and the steering gets pretty slack and slow. Without knowing the original fork length I'd mock the frame up with wheels and figure out a bottom bracket height/drop that seemed reasonable and go from there.

Rock shox did make externally travel adjustable forks called U-turn that had a knob you could crank the fork up and down with. They make this sort of thing super easy, I don't recall if they overlapped 1" being available.

I have parts to put together at least one Marzocchi in 1", and an extra 1" steerer tube. Would be a 63/70mm travel fork. If you can't find something let me know. Might also have parts for a 1" Manitou, but would be way more of a project.