Gabe, All of blitz clutches are made by ORC (Ogura Clutch). The part you're looking for is pretty easy to order. Any ORC dealer can get it for you. You are looking for the sleeve and bearing assembly for the ORC 559D twin clutch for S13/S14 SR20DET. The blitz part number is in their 07 Power Book, but i'm not sure if they can still get it since they changed over to the carbon clutches. Either way, i'm sure you can get the part from any ORC dealer. You can try Nengun performance or Bulletproof automotive. They can probably get it for you. Hope this helps.
http://www.paramo.jp/view_pamph.php?client_id=ogura&pamph_id=product200 6&page_no=1〈=en
go to page 16 (click on the right arrow)