Another good option would be skyway's 8"x 2" caster wheel (they really measure around 7.5"). They have light weight plastic hubs, 7/16 bearings, and a 4 lug bolt pattern that can be adapted to standard AM sprockets with a bit of drilling and a few standoffs. Also a wide range of tires are available with different material and tread options. I believe both 2753 and 469 used them this year (correct me if I am wrong on 469).
http://www.skywaywheels.com/products_004.htm (all the way at the bottom of the page)