Any old linear damper will do really. I've had good results with Ohlins and Hyperpro, and they are user rebuildable (if you have some mechanical skill). Meaning you can replace seals or oil at home with a minimum of tools - it doesn't need to be done that often.

Key thing to get right is length, I'll measure mine later from memory it was 280mm and I find it is just long enough with the steering restricted for racing.

Other than that a 41mm fork clamp (for std forks) is needed and make sure the frame mount has a rose joint/ball joint to allow for sufficient movement when turning.

Probably haven't helped much, with stating the bleedin' obvious.