Sound diffusers

I currently have CD racks at the first reflection points of my tower speakers (Von Schweikert VR-4 JRs) with the CDs spaced and staggered as diffusers. I would like to experiment with different diffusers when I move my CD racks. I’m cheap and am not willing to pay big bucks for commercial studio pieces. I also am not sure the cheap soft foam eggshell ones will be effective. I could buy those at Walmart. I think the diffusers need to be stiffer. I’m no good at woodworking or I would make my own. I know the brands GIK and Auralex are popular but I’m looking for something less expensive. Any thoughts would be appreciated.