Originally Posted by M.Lou.B

"Topeak does makes fork cages that come with the adapters for forks without mounting holes. I have these but do not use the provided mounts as my Surly Troll has cage mounts, so can't really vouch for how well the separate mounts work."

Thank you, that is gold info. I'll look into those.
Using adapter clamps, I could choose from a larger variety of forks and hopefully find something that's very similar in geometry to the old fork.

We're actually looking for two forks for two separate bikes, both 1 1/8" steer tubes, both have threaded forks with quill stems.
Mine is a Trek Multitrack 7300 (from 2000 or 2001) with a heavy CroMoly fork and a quill-to-ahead adapter. I'm hoping to shed some weight with a new fork that would allow for a true ahead built.
My partner's is an old but beautiful Bauer Trekking Line Dusty which we're restoring. The old suspension fork is completely rusted. We're planning a bike-packing built with drop bar conversion, ahead stem and a rigid fork. We've kept the old fork for reference.

Thanks for pointing out that swapping the fork may impact the entire geometry, steering and riding properties. We are aware,and we do hope to find something similar. If you've got any more information on what to consider when swapping the fork, that'd be really helpful.

Thanks again for your help, we really appreciate this!