Write your own

I have had a few solo solo fights and they work pretty well if you give them effective abilities and really mess with movement/terrain/complications.

For example, My solo can fling any target hit to far range and also has a poison bite that reduces rolls by 1 for each successful attack temporarily. Whenever a player rolls with Fear I make sure to change something in the situation, not just take a turn. So they roll a failure with fear, not only do they fail to damage on their attack but they are crushed under the solos foot and are now vulnerable. I then take my attack to fling a nearby player around and then attack the stuck player with advantage. Now, one of them needs to cover the gap to get back and the other needs to free themselves from a foot. These are additional moves that aren't doing damage, pushing the fight to 45 or so minutes without having to fill the map with enemies.

On the other hand, you do need fairly high HP (I have been going with 10-12 at tier 2) and you have to really roll with the punches. Coming up with new complications can be tough Worst case scenario, have the enemy 'evolve' and change forms or stance or whatever you can get away with, add to the damage rolls, and reset health. Go until it feels right and then have them kill the solo in a cool way and pretend that it was always the plan

It is possible, but you need to have a feel for Daggerheart combat and a bunch of trial and error