As other have indicated, there is no such thing as a suspension fork that will be an exact fit for this bike. Any fork with the same size steerer (1 1/8"?) will "fit" in the sense that it can be installed, but it'll be longer than a rigid fork to accommodate the travel. How much longer depends on how much travel the fork has. These days, I think 29er forks start at 100mm. You might find something older that is 80mm? There also might be some short travel hybrid bike style suspension forks designed for on-road riding that could work, though I don't really see the point of that.
Adding a longer fork will raise up the front end of the bike and change the way it handles. The more travel, the higher the front end will be. You can try to offset this by using a negative rise stem, but consider that a 100mm fork would add over 4" to the height of the front end, so even a super slammed stem setup would probably feel way too high.
Are you building something for a specific scenario? I'm curious to know what the max tire size is on the rear. Seems like it would be limited to 33m cyclocross tires, which would limit off-road riding scenarios where a suspension fork would be beneficial.