You can order most any flail mower parts from FLAIL-MASTER, 800-251-4020.
I have three of them, a 5', 6', 7'. The 6 footer was abused when I got it. I had to do some fixing up. It's still beat up, but cuts! The 7 footer has trail wheels. I have used it to mow high to knock off the weeds in a pasture. I have never experienced a problem with a flail mower consuming PTO power. When adjusted with the proper knifes they will cut every bit as nice, if not nicer, that most finish mowers.
I also use the 6' to cut weeds that are 5-6' tall on my manure pile. I usually leave the roller about 10" off the ground the first time, then lower it.
There's about a years reading (on just flail mowers)on another forum.