Well, at 1 inch your chances of finding a suspension fork will be slim to none. Let alone a suspension fork worth owning.

Try WoundUp. They have what you seem want: a non-suspension (rigid) fork with a steel, threaded, 1 inch 210mm steerer, straight blades. It'll run you about $650 and about 8-12 weeks or so delivered. They are good forks. I own 3 for various bikes.

Now would be the time to go the whole hog & upgrade to disc if you are going to blow that kind of money, already.

Custom steel forks from a frame builder like R&E Cycles will set you back around $500-$650 or so depending...

If it were me, in your situation with a 1 inch threaded steerer, I'd seriously consider a different bike if the plan was to take it anywhere rough. A whole new bike with suspension can be had for less than just the fork upgrade...

Or, a co-op for a generic random replacement fork & keep the bike as a rigid for cross country/single track/ urban use. Which is what the bike was likely designed for to begin with.

In short: Don't throw good money after bad. Your options are both expensive & limited for what you want to do.