You won't need the Simga22, you'll need a single rail PSU like the Sigma11 (as grawk suggested) or Tangent's STEPS, it just depends on how much you want to pay. I'm sure the Sigma11 or STEPS (with LM338, not LM317) will be very good for it, but you're looking at about $80 for either of those or about $40 for the TREAD, which I'm still sure will sound fantastic.
) sells kits for his TREAD as well as TREAD and STEPS boards. Amb (AMB Laboratories DIY Audio Site
) sells Sigma11 boards. I don't think anybody has kits for the Sigma11 (unless Jeff at www.GlassJarAudio.com
sells them, but I think he only carries the Sigma22 kits).
Either way, all parts for either PSU can be bought from DigiKey or Mouser with personal preference going to DigiKey because they have Panasonic FM capacitors which are basically the best bang/buck PSU caps (and pretty much best in general).