I also would think that a Surly fork for an Ogre or something would be a possible solution. I cannot recall if they still have the rim brake bosses still, but I also agree on thinking of setting up a front disc if you have a disc designed fork. I've used mechanical discs for years and any of the more established mech. options are a proven, well performing option.

Of course, changing out a fork will mean you should inform yourself very well in fork and frame geometry numbers and be aware of how putting on a different fork could change all kinds of parameters of your bikes riding and steering quality. In the past I briefly thought of changing the suspension fork on my old mountain bike for a rigid one, thinking I might use that bike for some long trips in Latin America, but in the end I got my Troll---but I never did seriously learn all about fork details and the impact of all the different rakes, wheelbase, etc etc, but I did read enough to be wary of how a poorly chosen fork replacement could mess up how a bike would ride, so be wary and well informed.

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.

https://www.topeak.com/global/en/product/1129-VERSACAGE

PS, what bike do you want to do the fork change for?