I found a place to purchase some 320 and 400 grit sandpaper rolls like you get from Rockler or Woodcraft. The place is called Wholesale Tool and the 400 grit paper you can get in either 1" or 2" wide strip by 50 yd rolls for $7 and $12. I bought the 2" wide roll and will rip it down the middle to make 100yds for only $12. They have 320 grit but in a different brand and it is more money costing $17 for a 1" x 50yrd roll. They also carry ther usuall lower grits but I didnt see any rolled grits over 400. They have stores throughout the US. I think their web site is www.wholesaletool.com