You're right about the hard to find used cultipacker. I happened to luck up and find one a few years ago in Cedartown, Ga. It sure helps the seeds make better, firmer contact with the soil for shallow planted grains and leaves the field looking neat.
I don't know anything about those wheels from Agri Supply but it sure sounds like the way to go. On a 5 footer you'd have about 26-27 wheels so that would be a lot less expensive than just buying one. That's what I was going to do before I found the one I got. Mine has 2 sections of rollers, larger rollers first followed by a row of smaller diameter rollers on back. It was built as a seeder but the boxes are missing and I'm just using it as a cultipacker.
It buries the smaller rocks as it passes over them and also helps with erosion by firming the soil. As far as how good it would hold up would be how fast you tried dragging it. Around here the bigger rocks would sooner or later break a wheel if you traveled very fast. I'm old and slow so don't worry much about it.
Tifton is the closest Agri Supply from here then Valdosta there also is one on I-16 before you get to Suvannah. I usually keep me a list going and stop in Tifton on the way to my Son's house in Fla. when I can make it down. If you build one don't forget to show us some pictures.