free standing diffusers

This looked like the most logical place to ask my question so... are there makers of free standing diffusres of approx. 55" (or a little more) and if so could you pont me to them? I hvae Michael Green's Room Tunes and I have Apogee Slant 6s that I use them with but the Room Tunes are a few inches shorter than the speaker height and I like to investigate an aleritive differ if there's some out there. Thanks for helping. :)